Introduction
This introduction, and honestly large parts of this article as a whole, are going to borrow heavily from Matt Collville/MCDM’s Strongholds & Followers. It kinda has to because, unless your GM does something else to incentivize it, there’s very little reason for players in most campaigns to do anything besides murderhobo their way through history, spending what often amounts to much less than a year going from a being that might lose a 1v1 with a goblin to something capable of talking to gods on a first name basis or rewriting reality on a whim. Because it’s much easier to write a story where you go to a place and do a thing, having a place to call your own is often impractical, uninteresting, or both depending on your table.
Older versions of D&D (mostly 1st and 2nd edition) just assumed that you would try to build a base at some point. Having never read or played anything before 3.0, I can’t really speak to why they assumed that, but I’ll certainly take Matt’s word for it. I will say that, for many people, there is something inherently satisfying about having a space to call your own that you have fantasy-game levels of control over (The Sims, Minecraft, etc), but that’s often more of a solo experience than something that makes for good cooperative storytelling unless you add mechanics to take it from “this is a castle-builder’s committee meeting” to “let’s have a reason to come to an agreement so we can get this done.”
With all of that said, we’re going to cover a little bit about how and why your theoretical base came into being, and then go over how to defend it. I already discussed Stronghold & Followers which was written for 5th Edition D&D, but I would also recommend picking up the Stronghold Builder’s Guidebook if you want a more granular experience around constructing the edifice itself. Do note that it’s a 3.0 product, so you’ll have to do some work with your GM converting the parts of it you care about, but I think you’ll be happy with the result if you do want to, for instance, add traps to your base.
Table of Contents
Why do you have a base?
I know this feels weird as a place to start, but the first thing to think about when you’re trying to defend something is “what is this and why am I defending it?” To that end, we really need to define what a base even is. In the broadest possible terms, anywhere you plan to rest needs some level of defending. Short rests are generally defended by the entire party being conscious and aware of any threats that approach them, although I suppose the Catnap spell exists and has maybe been cast once.
Mostly, then, this starts off as “how do we sleep through a night without getting eaten by wolves?” The answer is “create a rudimentary base.” Unless you’re a full party of elves (or Warforged I suppose), someone will have to sleep for 6 hours as part of an 8-hour long rest once a day. Now, technically speaking, the rules for Long Rests don’t say that your 6 hours of sleep have to be contiguous, so you could easily have a 4-person party where half the group sleeps in a 4-hour and 2-hour chunk and be perfectly fine just cycling through your 2 hours on watch. This has no verisimilitude whatsoever, but, then again, magic. Speaking of, the game provides several spells to protect you while you sleep, from the very basic but excellent Alarm to the very powerful Magnificent Mansion, with a broad range (Tiny Hut is an eternal favorite) in between.
Since it’s unlikely that your entire party is optimized for taking a watch shift, some amount of preparation is a good idea. Getting into a room in a dungeon with a single entrance that can be guarded, setting up hammocks well above ground, or even building a quick palisade with scavenged wood can all be helpful. Once you have those set up, congratulations, you have a rudimentary base.
But I digress
You’re probably not reading this to learn about how to make sure you don’t die in your sleep, though. You’re here because you have grand visions of a castle with your name on it…s deed, and you understand that strength invites challenge, so you want to prepare for if and when it gets attacked. Now we really need to circle back to the question of “why do you have a base?”
There’s a few main reasons people put up with the hassle. Maybe your group really wants a home for story reasons. If your story is more troubleshooting and less following a single quest chain, you need a place to be while you wait for the next thing to happen. Popular media gives us many great narrative examples of this: the Halls of Justice, Avengers Tower, even Camelot. This trope can even be expanded on to include less-traditional-but-still-possible-with-these-rules bases: Howl’s Moving Castle is an incredible movie and completely buildable using the Stronghold Builder rules mentioned above. Boats and roving barbarian camps have rules in MCDM’s book.
Maybe you were given a base, either as a reward for clearing it of hostile beings or for some other service to whoever laid claim to it before you. Maybe you just found some long-abandoned ruins and thought to yourself it would be nice to have a place to store your enormous piles of money you have nothing productive to do with. If this is the case, please talk with your GM extensively before you try applying these rules because they can very rapidly derail a game that isn’t supposed to be centered around the drama that comes with owning a castle.
Why did that matter?
Knowing why you have a base is going to be the primary factor from which flows the question “what are you defending the base from?” If you’re taking over a recently-constructed base, it was likely put there for strategic value that’s still important. That means it’s probably present as a defensive measure for something. That could be anything from defending against hostile people, to a cursed forest full of monsters, to a keep on the borderlands, to protecting a critical piece of infrastructure like a bridge. In fact, good bridges were such important and expensive endeavors that bridge castles (and bridge towers) have their own wikipedia pages.
Castles occupy a strange sort of space in high fantasy games because they’re really only good at one thing: providing a place for some people and possibly things to live that is hard for largeish groups of low-powered humanoids to get into. Anything with a fly, climb, or burrow speed (or anything that otherwise doesn’t care about mundane walls) will do an excellent job of circumventing your defenses, and please note that this list includes 3rd-level NPCs with spellcasting and 40 pages of monsters in dndbeyond. If you’re in your nice big open courtyard when a swarm of stirges comes to feed, you’re going to have a bad time.
This means that your base is going to need to be tailored to threats you’re likely to encounter. If you really are just out protecting against a horde of orcs, great. Have a normal castle. If you need to protect a trade route from harpies, you probably need something with less defenses and more people to shoot arrows. If you are the invading liberating army, you definitely need something mobile for a command center but still defensible enough to protect your important assets. Or maybe you just want to play with the powers granted by strongholds from the MCDM book, so all you’re really defending against is whatever happens to wander up to your tower/temple/keep/establishment, which might eventually include whatever BBEG you’ve made angry in your campaign.
Seriously Random, why?
Thank you for bearing with me for several pages worth of text to hear the answer: layout.
I was requested to write an article called “Practical Guide to Defending a Permanent Base,” and defending implies combat and intruders. Combat (at least in 5th edition D&D) is usually run on a grid of some kind, and layout becomes extremely important once you start trying to use magic to protect certain areas. Most of the spells that you could use to protect something have a limited area, so you’ll need to be conscious of those size limitations when laying out a base. I actually mentioned many of these in the Practical Guide to Wish because one thing that does make sense as a reason to build a place is retirement from adventuring.
Let’s start by looking at spells:
- Mighty Fortress is more of a way to create a stronghold than to protect one. It’s also an 8th-level spell, meaning you won’t have access to it until your character level is much higher than the 7 suggested by Strongholds and Followers as the right time for this endeavor to start.
- Guards and Wards is the quintessential “protect a building” spell. Each of the small versions of the buildings in Strongholds & Followers would nicely fit right around the 2500 ft2 of coverage it provides. That said, to make best use of the spell, you’d basically want to make a maze of criss-crossing hallways and doors because the Corridors section of the spell is easily the most powerful feature for preventing things from getting to a specific place.
With just 4 crossroads, you give someone trying to right-hand rule (or left-hand rule for you speedrunners) a chance that’s only slightly more common than rolling a natural 20 of navigating correctly. Bump that up to 7 crossroads and it’s less than 1% they make it through. Once they finally make it to the door you care about, place a Suggestion on it telling them to return to home as quickly as possible. This will make them burn any resources they have like spell slots to teleport out, or just get lost wandering through your maze again for 8 hours (since you’re not casting the Suggestion you don’t have to maintain concentration on it).
You also really want to have your base be in a cavern for this because it prevents any of the climbing/flying/burrowing shenanigans I mentioned (burrowing creatures usually can’t burrow through stone). Another possible option is to have your protected room be at the center of the maze; just make sure you have a thick floor and roof. - Druid Grove is intended to be Guards and Wards but for outdoors, but it is pretty awful on its own. It can cover up to a 90-foot cube which is about 10% more volume than Guards and Wards, but it’s also not shapeable and must be a cube. Combined with the fact that its only built-in applications specify they must be on the ground, it’s actually only 810 ft2 of coverage.
The effects are also just not good. If you could combine the Gusts of Wind with the Spike Growth you’d at least have effective ground control, but those are both on the list of a single thing you can attach to the spell. If you happen to be high enough level you can cast it twice in a day (level 13), you can cobble that together by placing a Gust of Wind at the edge of one area and a Spike Growth at the edge of the second area right next to it so you push from the area of one into the area of the other. By that point, though, your primary challenges are going to be things that aren’t going to care so much about having to walk over a cheese grater. - Temple of the Gods is closer to Mighty Fortress than Guards and Wards, but has some very useful effects. It does make a building, but the area can be huge (120ft to a side), so you could very easily just build other buildings inside it. It has some very nice effects for high-level characters like preventing a wide range of creatures from entering if they fail a Charisma save, and having a permanent Bane on them while inside even if they succeed. Also wonderful is that it prevents scrying sensors and divination magic, which makes you much more likely to be able to plan to deal with the BBEG wizard without them knowing what you’re up to.
- Hallow is the big area defense spell available to Clerics. It’s 5th level, so you get it not too far after the Stronghold Rules say you should be first getting your Stronghold. It has a 60-foot radius, which can easily cover the area of any of the Strongholds listed in the book, and is very much a thing you should remember and factor into your building plans when constructing one (if you construct one rather than inheriting it). It doesn’t have all of the effects of Temple of the Gods, but you can prevent any of the same creature types from entering. Especially good is choosing Silence on the affected groups because it will prevent them from casting Dispel Magic on your Hallow since Dispel has a verbal component.
- Forbiddance is the other half of Cleric protection. Prevent things from walking into your Hallowed area via teleportation or another plane. The area is huge and doesn’t need to be regularly-shaped, but probably needs to be contiguous based on the wording. If they just walk in normally, they start taking a pretty large amount of damage every turn until they leave or die.
- Private Sanctum takes several of the best parts of Temple of the Gods and Forbiddance and gives them both to wizards as a 4th-level spell. Just in case you needed a reminder of the favoritism given to the class that bears the game owner’s name. It is, unfortunately, also a cube, and unlike Guards and Wards, you can’t provide a password to ignore its effects. You also can’t ignore its effects yourself, so be very careful about where you place this. My recommendation is to build your teleportation circle slightly outside of your sanctum so that you can get the spell’s full benefits without breaking your ability to come and go as you please.
- Wall of Stone comes in very, very handy if you’re going to try to build a base yourself. With some patience, Wall of Stone, and Stone Shape (and the Mold Earth Cantrip if you feel like digging), you can quite easily create a very boxy but completely serviceable stone building in less than a week. Use this as the foundation for expanding into a whole stronghold with rules as listed in the book (I’d probably call this a “ruin” and start from there), or just accept that you’re going to have a weird-looking castle and go.
Layout
Ok, now that we’ve talked about all those spells, what should the layout look like? Well, since most of them specify a cube or radius, we should build in a square (remember that 5e handles “radius” by making squares, not circles). If you plan to have NPCs living in your stronghold, you should probably have some nod toward usability, but if you just plan to take care of it yourself, I’d definitely recommend the “maze with your private room at the middle” option to take best advantage of Guards and Wards. The idea of “Defense in Depth” is a real thing and you should apply it.
One thing worth mentioning is how you would defend a base with purely mundane methods. In this case, you’d really just want to look to historical castles for inspiration. One of the two books listed above taught me a new word: barbican. It’s the area between the outer gate and an inner gate to a courtyard between the walls of a fortification and the keep. I’d definitely make sure you have one of these if your story has you defending a castle for its traditional real-world use case. The barbican is an improvement on the Motte-and-bailey castle which was the gold standard across Europe for nearly 300 years because of their ease of construction and impressive defensibility. Fun fact: this is the etymological root for the modern word moat.
Ingress / Egress
In your chamber in the middle of your base, dig one square 5 feet down so that the ground-level cube you create with Private Sanctum won’t prevent you from teleporting (including Teleport but also just Dimension Door) in and out. I would really recommend this be underground or in a cave system that you reshape as you see fit via mining (magical or traditional) to avoid the 40 pages of monsters with alternate movement modes mentioned above. If you can do that, a Forbiddance will make it so nothing can cheese its way in by walking ethereally through walls, and so they’d have to know about the one 5-foot square you leave open for teleportation or walk through your whole gauntlet.
If you’re feeling extra paranoid about your own secret teleportation-only entrance, you can place other countermeasures on your teleportation chamber. Mundane traps, secret doors, and potentially a guardian monster like a golem or skeleton can all make certain that enemies lucky enough to find their way in will regret doing so.
If teleportation isn’t an option for you (you’re not a caster and haven’t found an item like a Cape of the Mountebank), you’ll need a mundane entrance. You know: a door. This door should be heavily defended. False entrances (think Tomb of Horrors) are a great option, and making the true entrance a secret door is very effective. Even so, security through obscurity is not an effective defense, so your entrances should include countermeasures for intruders.
Traps
Speaking of, you should install some traps if you’re going for “optimized hidey hole in the ground” rather than an actual lived-in fortification. 5e’s rules for crafting traps are one of the few places where you’d really, really like to push the bounded system on a skill check. Get your friendly 6th level Artificer (or possibly a Rogue with Expertise in Thieves’ Tools), get someone to throw a guidance on them, and get someone to use the Help action so they have advantage. Weirdly, the crafting rules don’t specify what ability you use, so I would say either Dex or Intelligence are perfectly acceptable. Now you just power them through a bunch of short rests and have them fill your labyrinth with a bunch of vaguely-described areas which deal 12-ish damage each.
Or, instead of just dealing damage, how about you add some spice to some of them with some magic items?
Magic Items
If one of your traps was, for instance, a pit trap, you could have the bottom of that pit be a Bag of Devouring. If any body part enters the opening, flip a coin. If the triggering creature loses the flip, it gets one chance at a DC 15 Strength check, after which it simply dies. No save, no effect to be immune to, it’s just eaten. Or, make your trap a pressure plate that drops a Dispelling Stone on someone. Just make sure to do that in an area that doesn’t contain any of your own 5th-level spells. How about doing the same trick with an Elemental Gem (or 10) and just summoning an awful army for your intruder to fight on no notice. Elemental Gems are only Uncommon, so they’re pretty quick and cheap to craft, especially for that Artificer friend.
Speaking of summoning an army, why not pick up a Horn of Valhalla? This is a great emergency distraction or perhaps even a way to turn the tide in a fight. There are versions at every rarity, but the one I think is the best bang for your buck (rare), will get you an average of 10 CR 2 berserkers once a week and, really, if your stronghold is getting invaded more than once a week you’re doing something wrong.
Last couple of utility things: carrying a Lantern of Revealing around while wandering your labyrinth is a great way to stymie anything trying to sneak around invisibly. If you happen to have a Bard friend, you can give them a Lyre of Building and enjoy having your structure be immune to one type of damage every round.
People
We just spent a lot of time talking about magical defenses, but NPCs can also be a valuable asset if your castle is, in fact, a castle and not a dungeon. This is what’s largely assumed for the Strongholds & Followers adventures because they have whole mechanics to deal with unit-based military encounters. I’d highly recommend checking out the mob combat rules or maybe even our Doom-style combat if you plan on running a large-scale siege encounter. Dozens of commoners with shortbows is an incredibly effective deterrent to anything that’s not much more powerful than a commoner with a shortbow.
Conclusion
It turns out that the real well-defended permanent base was the dungeons we were delving along the way. In fact, here’s what it looks like when I draw one in Dungeon Alchemist. With a total of 13 branching paths and 2 doors that are both Arcane Locked and look like the walls next to them thanks to Guards and Wards, this is the perfect getaway for a wizard who just wants to be left alone. I also made this map exportable to every virtual tabletop that Dungeon Alchemist can use; link to the zip file containing all of them here.
