Changelings have a hag mother, and inherit magical capabilities from their mother. Every one of them has heterochromia (two eyes of different colors), but I spent the time to check: there is still normal heterochromia in Golarion, so if you see someone with differently-colored eyes that may just have cool eyes rather than having a weird mom.
Mechanically, the Changeling is neat, but doesn’t offer a lot of outstanding options. There are options to support sneaky characters, melee builds, and a little bit of spellcasting, but you’re not going to use the Changeling’s Ancestry Feats to totally disregard your actual Ancestry so look for combinations between what your Ancestry normally offers and what you can get from the Changeling. As an example: both the Catfolk and the Orc have Ancestry Feats which allow you to apply Persistent Damage on a Critical Hit. You can combine that with the Changeling’s Cursed Claws feat and apply two types of Persistent Damage on one Critical Hit.
RPGBOT uses the color coding scheme which has become common among Pathfinder build handbooks.
- : Bad, useless options, or options which are extremely situational. Nearly never useful.
- : OK options, or useful options that only apply in rare circumstances. Useful sometimes.
- : Good options. Useful often.
- : Fantastic options, often essential to the function of your character. Useful very frequently.
Like many Versatile Heritages, the Changeling grants low-light vision, or Darkvision if your Ancestry already has low-light vision. This on its own is a great option, and even if you don’t take any Heritage-specific Ancestry Feats it can still be an impactful Heritage option for Ancestries which normally have poor vision options.
- Brine MayAPG: If you’re going to take this, why not pick an Ancestry/Heritage with a swim speed?
- Callow MayAPG: A great tactical option for builds which can capitalize on Flat-Footed targets such as rogues.
- Changeling LoreAPG: Trained in two good skills and also Hag Lore.
- Dream MayAPG: A trio of situationally useful effects. The overnight healing looks tempting, but there is an abundance of inexpensive healing options (Focus Spells, the Medicine skill, etc.) which make overnight healing a mostly negligible part of hit point restoration, Drained/Doomed effects aren’t common.
- Hag ClawsAPG: Basically daggers. These are pretty standard for ancestry feats which grant claws. If you’re building around Strength, consider Slag May instead.
- Hag’s SightAPG: If you don’t already get Darkvision between your Ancestry and the Changeling Heritage traits, this is an absolute must. The ability to see in darkness is simply too good to pass up.
- Maiden’s MendingAG: Out of all of the published Changeling Ancestry Feats, there are enough to get exactly two qualifying spells at character levels 9 and 17. Even if these temporary hit points didn’t expire abnormally fast, this feat would be bad.
- Moon MayAG: Guidance is great on any character, and it doesn’t care about your ability scores or proficiency. It’s a perfect innate cantrip.
- Slag MayAPG: A good natural weapon for Strength-based builds, and the fact that the claws are cold iron helps to overcome damage resistances which are typically hard to handle without manufactured weapons.
- Snow MayAG: Very situational.
- Veil MayAG: Too situational. Cast Illusory Disguise.
- Virga MayAG: Great for Charisma-based Occult spellcasters (Bards, Sorcerers, etc.). Electric Arc is among the best offensive cantrips, but it’s not on every spell list.
- CalledAPG: Nearly all effects which target Will are mental, so this is an easy +1 bonus to nearly all Will saves. The additional benefit against effects which make you Controlled is neat, but since it only takes effects when you’ve already succeeded it’s not very impactful.
- Cunning HairAG: Very situational and extremely limited.
- Favorable WindsAG: Wind is almost never an issue. If your ranged weapon has a 10-foot range and that’s a problem for you, get a weapon with a better range increment.
- Mist ChildAPG: The increase isn’t huge, but if you’re consistently relying on concealment or stealth in combat it will pay off over the course of your character’s career. As an example, druids with Order of the Storm can already see through fog, and combining that capability with Mist Child puts you at a strategic advantage over your foes. However, remember that your allies need to make the same Flat Check to target you, which may make it difficult to receive buffs or healing.
- Accursed ClawsAPG: Persistent damage is really good. It would be nice if there was some sort of scaling, though. If you can get other similar effects, such as the Catfolk’s Aggravating Claws, you can stack a bunch of persistent damage effects.
- Invoke the ElementsAG: A great defensive buff. If enemies stay at range, they have trouble hitting you. If they get into melee, they take damage. Only once per day, unfortunately.
- Mother’s MindfulnessAG: Excellent for durable front-line builds or characters with valuable but frail pets (familiars, etc.). Be sure that you have enough hit points to survive using this repeatedly.
- Occult ResistanceAPG: +1 to saves against one in four spells.
- Hag MagicAPG: A great concept, but the spell options aren’t great, and most won’t be effective unless you’re a Charisma-based Occult spellcaster.
- Spiteful RakeAG: Dazzled imposes a 20% miss chance on the creature’s attacks, which is huge for big martial enemies. If you’re lucky enough to crit and leave Dazzled in place, your party is at a huge advantage.