Pathfinder - Practical Guide to Familiars
Last Updated: January 29th, 2019
Familiars in Pathfinder aren't the combat pets that they could be in 3.5, but they are certainly no less useful.
Ultimate Campaign includes some wonderful content about how to handle pets in your game. Reading it isn't essential, but it may improve your play experience when pets are involved.
- Evolved Familiar: The prerequisites are frustrating, and evolution points aren't as useful for familiars as they are for other pets which do more fighting like an Animal Companion. :
- Improved Fortitude: Your familiar shares your saving throws.
- Iron Will: Your familiar shares your saving throws.
- Lightning Reflexes: Your familiar shares your saving throws.
- Toughness: Your familiar has half of your maximum hit points.
Familiars in the Party
Because Familiars determine their abilities based on their master's hit points, BAB, and skills, familiars can fill many roles in the party as well as or sometimes better than their master.
Common among spellcasters who make no effort to capitalize on their Familiars, a basic Familiar is still an excellent tool. They can serve as a delivery mechanism for touch spells, and because of their small size and good Dexterity they are often excellent at Stealth, allowing them to move into position to attack before the party kicks in the door. They can also act as couriers for Exploding Runes and Sepia Snake Sigil, or for delivering messages non-magically to nearby recipients.
If your GM allows it, your Familiar may be able to use magic items, especially if you have Use Magic Device. This can make your familiar extremely useful if you hand them wands of Cure Light Wounds, or scrolls/wands offensive spells which don't allow saving throws, like Grease.
Remember that Spell Trigger items like wands and Command Word items both require that the user be able to speak, which limits your options to familiars which can speak like the Raven or the Thrush unless you take Improved Familiar or get items like a Ring of Eloquence.
Especially useful if they have opposable digits, familiars can serve as Scouts nearly as well a Rogue. They lack Trapfinding, and can't get the ability from their master, so be wary of traps.
The exact mechanics of other skills are somewhat suspect. A wizard's familiar gets the same modifier to Knowledge skills, but I don't think any reasonable GM would allow a familiar to make a Knowledge check. Similarly, if your familiar can speak you might be able to use your familiar as the party's Face if your GM allows it. You might also let your familiar make spot/listen/search checks by itself, but the ability to provide the Alertness feat seems to be intended to reflect your familiar aiding you.
The biggest reason to pick up Improved Familiar (or any of the other special familiar feats) is because you want to turn your familiar into a fighting animal. There is a fantastically long list of wonderful options (see "Expanded Familiar Options", below), many of which can be very capable combatants. Because familiars use their master's BAB and calculate their HP based on their masters, combat familiars generally work best for combat classes like Duskblade and Hexblade.
Basic Familiar Options
Basic familiar options are available to Sorcerers, Wizards, and Witches by default.
|Archaeopteryx||Master gains a +2 bonus on Reflex saves.||B4|
|Bat||Master gains a +3 bonus on Fly checks||CRB|
|Cat||Master gains a +3 bonus on Stealth checks||CRB|
|Compsognathus||Master gains a +4 bonus on Initiative checks||B2|
|Dodo||Master gains a +4 bonus on Initiative checks||B4|
|Donkey Rat||Master gains a +2 bonus on Fortitude saves||UM|
|Fox||Master gains a +2 bonus on Reflex saves||UM|
|Goat||Master gains a +3 bonus on Survival checks||UM|
|Greensting Scorpion||Master gains a +4 bonus on Initiative checks||UM|
|Hawk||Master gains a +3 bonus on sight-based and opposed Perception checks in bright light||CRB|
|Hedgehog||Master gains a +2 bonus on Will saves||UM|
|House Centipede||Master gains a +3 bonus on Stealth checks||UM|
|King Crab||Master gains a +2 bonus on CMB checks to start and maintain a Grapple||UM|
|Lizard||Master gains a +3 bonus on Climb checks||CRB|
|Monkey||Master gains a +3 bonus on Acrobatics checks||CRB|
|Octopus, blue-ringed||Master gains a +3 bonus on Swim checks||UM|
|Otter||Master gains a +3 bonus on Swim checks||B3|
|Owl||Master gains a +3 bonus on sight-based and opposed Perception checks in shadows or darkness||CRB|
|Pig||Master gains a +3 bonus on Diplomacy checks||UM|
|Platypus||Master gains a +3 bonus on Swim checks||B4|
|Raccoon||Master gains a +3 bonus on Sleight of Hand checks||B3|
|Rat||Master gains a +2 bonus on Fortitude saves||CRB|
|Raven||Master gains a +3 bonus on Appraise checks. Speaks one language of its master's choice as a supernatural ability.||CRB|
|Sloth||Master gains a +3 bonus on Climb checks.||B4|
|Scarlet Spider||Master gains a +3 bonus on Climb checks||UM|
|Snapping Turtle||Master gains a +2 bonus on Fortitude saves||UM / B2|
|Thrush||Master gains a +3 bonus on Diplomacy checks. Speaks one language of its master's choice as a supernatural ability.||UM|
|Toad||Master gains +3 hit points||CRB|
|Tuatara||Master gains a +3 bonus on Survival checks.||B4|
|Turtle||Master gains a +1 natural armor bonus to AC||UM|
|Viper||Master gains a +3 bonus on Bluff checks||CRB|
|Weasel||Master gains a +2 bonus on Reflex saves||CRB|
The worst flying familiar, the archaeopteryx is fast and can fly, but it has poor maneuverability and an ability which makes its flight even worse. It has no notable special abilities. If you want something that flies, the bat, hawk, and owl are all better options.
With flight, low-light vision, and blindsense the Bat is a portable sensor. Once your familiar gains the ability to speak to you at level 5, it can locate nearby invisible enemies and point them out for you and your allies to attack. The bonus to fly is largely worthless (you need to make fly checks about as often as swim checks), but it doesn't hurt to have..
An octopus is a scary predator to its prey, but when most things are medium (and therefore bigger than the octopus), its Grab ability is worthless. The blue-ringed octopus's poison is very weak, and doesn't make it any more effective.
Hilariously effective at killing 1st-level Commoners and other weak humanoids, the cat is a good generic familiar. Cats get racial bonuses to stealth, making them excellent Scouts if their master doesn't invest in stealth. Unfortunately the +3 bonus to Stealth will be wasted on most spellcasters, but Arcane Tricksters and other Rogue/Caster hybrids may enjoy having a cat. Cats also have Scent, which allows them to detect nearby creatures.
The compsognathus is fast, has low-light vision and scent, an grants a +4 bonus to initiative. It lacks any useful skills, and its poison is very weak. As a familiar it's unremarkable, but the +4 bonus to initiative makes it appealing.
The dodo is Small, so it can threaten squares, carry tiny riders, and attack into adjacent squares, but it's otherwise really useless. The +4 bonus to initiative is fantastic for spellcasters, but there are several other (and better) familiars which provide the same bonus.
The donkey rat strongly resembles the normal rat. Donkey rats are Small (and can therefor threaten squares, carry tiny riders, and attack into adjacent squares), they're slightly less stealthy than normals rats, and they lack a climb speed, but they have slightly better perception than rats, and have the same special senses (Scent, low-light vision), and double the rat's land speed. Assuming you don't want to keep your familiar in your pocket when you're not using it, the donkey rat might be a minor improvement to the rat.
Decent stealth, decent perception, and Scent. The fox is a decent, though not very exciting, choice. It trades the rat's versatility for a better default perception bonus, so if your party is good at perception the rat is a better choice.
The goat is small, which allows it to threaten adjacent squares, but its attacks aren't good enough for it to be a viable combat option. The goat doesn't have any useful abilities, and the bonus to survival is probably waster on you.
Less versatile than the scarlet spider, and with an even weaker poison, but +4 initiative is so useful that you might take this solely for the initiative bonus.
With a +13 to perception, the Hawk will easily outstrip its master's perception checks until mid levels, even with the +3 bonus to Spot from having a Hawk familiar. Hawks fly, which is great for delivering touch attacks, but other flying options are better at stealth (owls) or can detect invisible creatures (bat).
Adorable, but totally useless. Even the +2 bonus to Will saves is bad because spellcasters nearly always have good Will saves.
Only useful for polymorph builds that intend to use grapple forms.
The house centipede is fast and has darkvision (like every vermin), and its poison dazes targets, which is absolutely fantastic. The bonus to Stealth can be nice for stealthy casters, and the centipede's +19 stealth is impressive. The poison DC is half of the centipede's HD plus its constitution modifier, but with only 10 constitution it will never be particularly effective.
The lizard has no redeeming qualities except a climb speed, and plenty of familiar options have climb speeds.
The monkey has human-like hands, so it can do cool things like hold and use weapons and magic items, making it one of the best Apprentice Familiar options available without Improved Familiar. It has a climb speed, but doesn't have scent and it's not particularly stealthy or skilled. If you are skilled (Rogue/caster hybrids typically are), the monkey can be a fantastic assistant.
Adorable, but only useful in an aquatic campaign, and if you're in an aquatic campaign you probably want something that can breath underwater.
Basically a stealthy version of the Hawk, and the Owl's Spot bonus applies in dim light conditions, like those common to dungeons.
At small size, the pig can carry a tiny rider (such as a Halfling affected by Reduce Person), and threatens adjacent squares, but it's certainly not going to win any fights. It has Scent, and the +3 to Diplomacy checks is nice, but it has to compete with numerous better options which provide Scent and with the Thrush, which can fly.
Only useful in aquatic campaigns, and even then there are much better options.
Slightly stronger and slightly faster than the rat, but considerably less stealthy and lacking the rat's swim speed. A bonus to Sleight of Hand is also considerably less helpful than the rat's bonus to Fortitude saves.
The rat is stealthy and has both climb and swim speeds, allowing it to get around a lot of places unnoticed. It has Scent and low-light vision, allowing it to help notice enemies. While it's certainly not exciting, the Rat is a great baseline from which to measure other familiar options. The bonus to Fortitude saves is also great for arcane spellcasters who typically have poor Fortitude saves.
If you want to be talkative, the Thrush's bonus to Diplomacy will be more helpful. Appraise is garbage. However, because the raven can speak it may be able to use magic items.
Mechanically very similar to the viper, but its poison deals Strength damage instead of Constitution damage, making it considerably less effective. It also has high Acrobatics, allowing it to more easily enter enemy's squares, and it's an excellent climber.
Iconic for being slow, the sloth's stats are true to its species. It is slow, its attacks are garbage, and its only redeeming quality is Scent, which you can find on plenty of other familiars.
The snapping turtle is slow, and doesn't really have anything special but Scent. If you want something with Scent you can do considerably better.
Basically a smaller raven, so it's harder to notice and to hit, but it's also less capable of carrying things. The ability for your Thrush to speak is situational, but if you're playing a Face the +3 bonus to Diplomacy can be really nice. The Thrush is one of only two basic familiars which can speak, which may allow it to use wands.
Dismally slow, no useful abilities, and 3 hit points is garbage. It can't even swim. Somehow the toad gets a +21 to Stealth, but the ability to sit still and not be noticed is not enough to redeem the toad.
Basically a lizard (but technically a dinosaur!), the Tuatara has both low-light vision and Darkvision, but is otherwise just a scaly weasel. A Survival bonus is very hard for most spellcasters to use.
Though the snapping turtle is technically stronger, both turtle are bad enough that they are functionally identical. The natural armor bonus to AC might be appealing for melee casters and polymorph builds, but I'm not certain if it stacks with other natural armor bonuses.
The viper's big appeal is its poison. The poison's DC scales with your familiar's effective hit dice, but with only 10 constitution you're going to have a lot of trouble getting enemies to fail their saving throws. You may be able to harvest poison from your familiar if someone in the party can use it. Also note that in Pathfinder, multiple doses increase the save DC of poison affecting the target by 2 instead of forcing separate saves, so you may be able to improve the poison's usefulness by applying it multiple times.
A climb speed and scent are the weasel's biggest advantages, but the Rat has those plus a swim speed, and Reflex saves aren't as important as Fortitude saves. The Attach special ability is amusing, but in practice it won't do anything useful.
Improved Familiar Options
Improved Familiar provides numerous additional options from multiple sources.
The paracletus has very few spell-like abilities, but has Commune 1/week like many improved familiars. Its big draw is the Emotion Aura, which can replicate the effects of Bless/Bane, provide a bonus (or penalty) so some social skills, or provide a +2 bonus or -2 penalty to willl saves. Because the paracletus is a bunch of floating stuff, it doesn't have limbs with which to manipulate magic items.
The silvanshee has some really great abilities. It has DR and some nice resistances, and is an excellent flyer. Coupled with a fantastic +19 Stealth bonus and its version of gaseous form, it's a really great scout. The silvanshee's spell-like abilities are all utilities, so they will remain useful long after other familiars spell-like abilities stop working due to their low DCs. Between Speak with Animals and Truespeech is can act as a translator to most creatures. The silvanshee also has Pounce for some weird reason, and heroic strength allows it to have the strength of an average human for an entire minute, making it more lethal than a typical cat. It also has Lay on Hands for 1d6 1/day, but the stat block specifically says always as a 2nd-level paladin so this healing won't scale as your familiar gains hit dice.
The almiraj's only interesting ability is that its horn can petrify things it kills. This will probably never be useful.
The cassisian is an interesting support option for melee casters. Aid provides a nice buff, and the cassisian's Lesser Protective Aura provides a small bonus to saves and AC, but the aura can be easily replaced with some relatively cheap items. Because the cassisian lacks limbs, it can't manipulate and use magic items.
The harbinger has some nice utility spell-like abilities, and can cast cure light wounds 3/day, but it has less abilities and weaker defenses than the tripurasura. Because it's a collection of floating components, it doesn't have hands with which to manipulate magic items.
The tripurasura has darkvision and constant detect magic, giving it slightly less ability to detect things than many comparable improved familiars, but its strengths lie elsewhere. It has DR and fast healing, making it plenty durable, as well as some nice resistances and immunities. The tripurasura's spell-like abilities are all utility options, which means that they will always remain useful long after other familiars DC's have stopped working. It can also manipulate items and speak, which may allow it to use magic items.
The lyrakien is a fantastic flier at 80 foot speed and perfect maneuverability. It has darkvision, low-light vision, and constant detect evil and detect magic effects, allowing it to locate enemies easily in a variety of situations. It has a handful of spell-like abilities, but their DCs won't remain effective for long. Cure light wounds is always useful, but at 1/day it can be easily replaced by a wand. Like many improved familiars, the lyrakien can cast Commune 1/week without the 500gp material component. The Lyrakien's Starlight blast will be almost immediately useless, and Traveler's Friend is very situational.
I can't really assess the beheaded because nothing specifies if you can apply the beheaded special abilities to your familiar. If you can there are some possibilities, but without them the beheaded is worthless. The highest CR familiar is CR 2, so you might be able to apply as many as 6 abilities (remember that CR below 1 works in steps: 1/3 > 1/2 > 1 > 2).
The brownie is slow, has no special movement types, and its special abilities are limited to a handful of poor spell-like abilities. It is only marginally better than a monkey. At the very least it can speak and manipulate objects, so it can probably use magic items.
I don't even know what to do with the carbuncle. It's a hilarious creature with some ridiculous abilities, but it's certainly not powerful. I kind of want to bring one into a party just to use Specious Suggestion on my party members, but I wouldn't want to bring this thing into a fight.
The cacodaemon is roughly equivalent to the quasit and the imp, but without limbs it can't manipulate and use magic items. Its signature ability to create soul gems is an interesting mechanic, and can be useful if you have other evil outsiders in the party, such as an Antipaladin's fiendish companion or an outsider summoned with Planar Ally.
The demon equivalent of the imp. It's abilities are largely equivalent, but the quasit can't see in magical darkness and can't gain abilities equivalent to the imp consular.
An iconic familiar of evil spellcasters, the imp is a decent option. It flies, it can see in magical darkness, it has DR and fast healing, and it has some spell-like abilities, including Commune and Invisibility (self-only) at will. It has poison, and a +2 racial bonus to the DC in addition to the normal hit die progression, but the ability damage is pitiful. The Imp Consular adds the ability to transform into tiny or small animals, and to communicate telepathically. Because they can manipulate items and speak, they may be able to use magic items.
Basically a larger and faster rat. These improvements don't really help the rat, and they're certainly not worth the cost a feat.
The Doru can fly, and can see in any type of darkness. It has telepathy to communicate silently with the party, making it a great way to get around quietly in the dark. It can make itself invisible, further improving its ability to move around unnoticed, and it can cast Commune 1/week without paying the 500gp material component cost. Unfortunately, its other spell-like abilities won't do much good and its poison is very ineffective. In essence the Doru is a bad version of the Imp.
The faerie dragon is an excellent flyer, but its spell-like abilities are weak and its breath weapon's 5-foot range is useless.
The shadow drake is really only useful in parties that depend on fighting in the dark. If you like to abuse spells like Darkness, the shadow drake is a good thematic choice, though it doesn't have a lot of abilities to throw around.
Elemental, Small (any type)
Elementals are combat familiars. At small size they can all threaten adjacent squares. Many have special movement types and effects on their attacks. They can all speak and manipulate objects, so they may be able to use magic items.
- Air: The air elemental's only interesting ability is flight, and you can get that from many better familiar options.
- Earth: The worst and most boring of elementals, the earth elemental doesn't even have an ability to add to its attacks.
- Fire: Burn is the fire elemental's big draw. The save DC for burn goes up with your familiars effective his dice, but the damage is small.
- Ice: Numbing cold is the ice elemental's big draw, but with such a terrible DC it won't affect anything interesting.
- Lightning: Spark Leap makes the lightning elemental a bit more effective against NPCs, but at small size it will still have trouble being effective with combat maneuvers.
- Magma: All of the tricks of both earth and fire elementals, and all of their problems.
- Mud: Entrap is a cool ability, and the save DC goes up with your familiars effective his dice.
- Water: The water elemental's only useful ability is Vortex, which is crippled by its small size.
The aligned creature templates are decent templates, but none of the base familiar options are viable in combat, so the templates are largely wasted.
The aligned creature templates are decent templates, but none of the base familiar options are viable in combat, so the templates are largely wasted.
The aligned creature templates are decent templates, but none of the base familiar options are viable in combat, so the templates are largely wasted.
The nuglub is an interesting option for a combat familiar. Its natural attacks have Grab and Trip, and it gets a racial bonus to Trip attempts. With such poor Strength those attempts won't go very far, but with a high BAB master (such as an Eldritch Knight), it might be able to put its attacks to good use. At small size it threatens adjacent squares, which means it can serve as a somewhat mediocre defender. It also has 120 foot darkvision, allowing it to spot enemies in the dark long before they can spot the nuglub.
The homonculus is a good flyer with a weak sleep poison. It is telepathically linked to its master, which is helpful for scouting, but it has no special abilities to speak of. Because it can't speak, it can't use magic items, so any number of other flying improved familiar options will be more useful. In addition, the homonculous must first be crafted using the Craft Construct feat at a base cost of 1050gp. The homonculous's one interesting ability is that you can add additional abilities to it surgically. While these extra abilities are tempting, they are far too expensive for their effects, and the cost of an additional feat to make the homonculus makes it a horrifically expensive option with no major payoff.
The arbiter his a decent flyer, and it has DR and regeneration, but very few useful abilities. It can cast Commune once per week (like many other improved familiars), but its other abilities are all unremarkable. It speaks truespeech (effectively the same as a constant Tongues effect), so it can serve as a translator, and because it has hands it may be able to use magic items. Altogether not awful, but there are improved familiars with similar capabilities and useful spell-like abilities.
Amusing and useful as a cheap scout, but garbage as a familiar. Spend the 25gp to create a bunch of them and use them as disposable scouts. The Visual Sensor ability works even if the creature isn't your familiar.
The shikigami is a garbage catapult. It likes to run around and throw improvised weapons at people. It can turn itself invisible or into a statue at will, and with darkvision it's a decent scout. It can speak and manipulate items, so it may be able to use magic items.
The augur is a good flyer, and it has regeneration and DR, but that's the limit of its unique abilities. It can cast commune 1/week without the 500gp material component, but plenty of better options can do that too. It can't speak and doesn't have hands, so it can't use magic items.
None of the mephits are particularly good. They have hands and can speak, so they can use magic items, but their abilities are all terrible.
The nycar's only interesting quality is regeneration. It can't fly, it's only extra move speed is a swim speed, and it has no effective offensive abilities. Its description says that it has forearms, but because it can't speak it still can't use magic items.
The spirit oni is a decent flyer, and it can turn itself invisible at will. You can wear it, which is a cute trick, but doing so isn't very productive. It can also cast commune 1/week without the 500gp material component, but none of its other spell-like abilities will be effective. It has fast healing 2, but with no reason to get into combat it isn't very useful. With no hands it can't manipulate magic items.
It can't fly, and it can't manipulate items. It doesn't have any remarkable special senses, and its spell-like abilities aren't very good. The pipefox's best qualities are that is is diminutive, and its constant comprehend languages effects.
The pooka is a good flyer, and with darkvision, low-light vision, and the ability to cast invisibility on itself at will it's a fantastic scout. With DR and fast healing, the pooka is fairly durable. Unfortunately, the pooka's other spell-like abilities won't be effective by the time you get improved familiar. Pooka can speak, so it can probably use magic items.
The voidworm is a great flyer. It has blindense, darkvision, and constant Detect Law. It has fast healing and some resistances, making it fairly durable. It can also cast commune once per week without the 500gp material component. Despite the ability to speak, it doesn't appear to have limbs with which to manipulate magic items.
Pseudodragons are good flyers, and their poison inflicts sleep. They have Darkvision, low-light vision, and Blindsense with an impressive range of 60 feet, and with telepathy they can silently alert you and your party to the presence of undetected enemies. Because it can speak, the pseudodragon can probably use magic items like wands.
The nosoi has good flight, darkvision, low-light vision, and spiritsense (which is a bit like a limited version of blindsight). It has a few resistances and immunities, and with the ability to make itself invisible at will it is great at getting out of dangerous situations. With +17 stealth and invisibility, it also makes a great Scout, and spiritsense allows is to locate invisible creatures. Speak With Dead provides some wonderful utility if you think to use it on something intelligent, but the nosoi's other spell-like abilitie aren't great. The nosoi's haunting melody is a cool ability, and as a familiar its pool of rounds per day are based off of your spellcaster levels, granting it lots of performance time. The DC scales with your familiar's effective hit dice, which can keep it useful for a long time.
Be sure to check the Psychopomp Subtype general rules.
I have no idea what these things are, but they're disgusting. They have six legs, but have a constant magical fly effect. They have DR, and either immunity or resistance to all four of the common energy types, making it fairly durable. The cythnigot has darkvision and constant detect law and detect magic effects, making it useful for locating enemies. It can also cast Commune once per week without the 500gp worth of material components, granting you access to essentially metagame information on a regular basis. Unfortunately the cythnigot's horrific presence and spores abilities have terrible DCs, so they won't be helpful in combat.
The raktavarna is a really interesting creature. It has the ability to change its appearance, making it fantastic for infiltration. Its poison deals wisdom damage and modifies the victim's memories, potentially allowing the raktavarna to continue to poison the target until it falls comatose. It has Darkvision, constant detect magic, and both climb and swim speeds, allowing it to remain useful in a variety of locations. Comprehend languages helps reduce your need for Linguistics or magical translation, and with DR and SR it's protected against weak enemies. Master's Eyes removes the need to scry on your familiar, and makes it much easier to rely on your familiar as a Scout. It can also cast Commune once per week without the 500gp worth of material components, granting you access to essentially metagame information on a regular basis.
The ratling is fantastic. It has good speed, including a swim speed, a climb speed, and an exceptionally rare burrow speed. It has both darkvision and low-light vision, and a constant detect magic. With +16 stealth and the ability to cast invisibility on itself 3/day, it's a fantastic Scout, and with dimension door it can reach distant locations without the need for flight. It has a constant Tongues effect, removing the need for your party to invest in Linguistics. It can also cast Commune once per week without the 500gp worth of material components, granting you frequent access to essentially metagame information. In combat its bite inflicts bleed, and it deals 1d6 of sneak attack damage. On top of all of that it can cast spells from scrolls as if it had the spell on its spells list, allowing it to use scrolls provided by its master to supplement your spellcasting abilities, and granting arcane casters access to useful divine spells. The ratling's only limitation is that its master must be Chaotic Evil.
The sprite is a fantastic flyer, it can be a permanent source of light, and it can detect evil and detect good at will, but that's the limit of the sprite's relevant abilities. It has a handful of spell-like abilities, but the only one that your caster can't already do at will is Color Spray, and with a DC of 11 it's not going to do much good 1/day. The sprite is a great concept for a familiar, but it probably isn't good enough to justify spending a feat.
The stirge attacks as a melee touch attack, so it can charge into melee and hit some of the toughest enemies without issue. Unfortunately it only deals one point of damage per round, during which time its AC is only 12, making it extremely vulnerable to retaliation. Then, once it's done feeding it's useless until it finishes digesting. The rules entry doesn't mention how long it takes the stirge to digest, but it's probably a few hours at least, if not a full day. Beyond Blood Drain, the stirge is a mediocre flyer with Darkvision and Low-Light Vision, which can make it a decent scout in dark caves and dungeons, but a Bat will be more effective.
An interesting combat familiar option, the Zoog has three attacks (one of which inflicts Bleed), and can affect incorporeal enemies. It has constant Detect Magic and Speak With Animals running, which offers some utility options, but Detect Magic is typically available to every spellcaster. It also has low-light vision, darkvision, and Scent, allowing it to watch for enemies in nearly any situation. The Zoog is severely limited by its Tiny size, which requires it to move into its enemy's space to attack, which makes it difficult for the zoog to perform meaningfully in combat.