Sibriex Lairs and Minions for Dungeons & Dragons Fifth Edition

I’m a little late posting this following Keith Ammann’s latest Sibriex tactics post, but it’s been a nutty week (I leave for Mexico on Friday). Anyways, let’s take a look at the Sibriex and see what sort of minions and lair this guy needs.

What is the sibriex?

If you’re not familiar with the sibriex, pick yourself up a copy of Mordenkainen’s Tome of Foes. Basically, the sibriex is a lesser demon factory. It uses an innate warp creature ability to turn souls (and other unfortunate beings) into abyssal wretches or rutterkin, which more or less look like that dude that fell in the toxic waste in the first Robocop movie.

They’re particularly nasty buggers and tough as hell, too, coming in at a solid Challenge Rating 18. With that high of a CR and legendary actions to boot, this makes them minor bosses for a group of 13th-level characters, or a super challenge for characters 11th or 12th. Much of the challenge will depend on how well equipped the party is to handle the sibriex.

Keith covers most of the sibriex’s tactics and strategies in his awesome article which you can read here: sibriex tactics.

What are a sibriex’s weaknesses?

When planning for support, it’s important to create creatures that complement the monster and make up for its shortcomings. Granted, as a high CR legendary creature, the sibriex doesn’t have a ton of disadvantages, but there are a few that should be addressed:

  • Sibriexes have terrible Strength and Dexterity. Granted, their magic resistance and legendary resistance will give it an edge against these sorts of attacks (and players should never know that legendary resistance is a thing if a possible), but it still doesn’t want to get caught frozen by telekinesis or hit with some other attack that limits its ability to do things. And let’s not forget that its shite Dexterity is pretty much going to guarantee that it’s going dead last in initiative order. However, its legendary actions are there to make up for that
  • Their hit points aren’t great, either. Despite a high Constitution, sibriexes only have 150 hit points. If these guys get hit with a well-placed paladin smite–let’s say with a +1 greatsword using a fourth level spell slot–they could lose 30 hit points in one shot. Worse yet, if a monk wails on it and forces it to make repeated Con saves (which, despite its +6 natural Con save bonus, the sibriex is not proficient with Constitution saving throws). But that’s not even the biggest fear it should have. With a melee combatant up in its grill, if a rogue is able to snipe at range, it will get an auto sneak attack for having an ally adjacent to the sibriex. That’s another 35+ damage right there. Suddenly, the BBEG loses half its health in one round.
  • They have no exit strategy. Sibriexes are one of the few monsters at their level that aren’t equipped with dimension door, plane shift, etc. Keith mentions they’d run if they got down to 60 hit points or less. But run where? (I address that in a moment.)



Sibriex support monsters.

The trouble with giving the ol’ sibriex lots of support monsters is that it’s already a Challenge Rating 18 creature. Adding only two CR 1/4 abyssal wretches to the battle bumps its XP from 20,000 to 40,000 when calculating combat encounter difficulty effectively taking it from a deadly 13th-level encounter to a deadly 17th-level encounter. 17th level is near-legendary for most characters, so the fear of getting turned into an abyssal wretch goes out the window when dealing with PCs at that tier.

If using support monsters, the best options are going to be weenies that act like speed bumps, slowing the characters down so the sibriex can use the full extent of its action economy for a few rounds. Trouble is, any self-respecting cleric is going to have its spirit guardians up and running in order to tear through weenies without hardly noticing them. Spirit guardians deal 13 radiant damage on average on a failed save (which all weenies will probably fail), or 6 on a successful one. That’s with just a 3rd level slot. When wandering the twisting passages of the Abyss, a cleric might even juice up his guardians with a higher slot. So it could be dealing up to 40/20 radiant damage. Might be a waste of a 9th-level slot to do this, but hey… if you’re literally going to “hell”, might as well pull out the big guns, right?

Fortunately, abyssal wretches, the obvious support monster for sibriexes, come with 18 hit points. So unless a cleric rolls better than average, they should be able to tie some characters up. With AC 11 and a +3 to hit with an attack that only deals 5 damage, it ain’t like they’re going to be doing much else.

If a sibriex comes with a squad of 5 abyssal wretches, that’ll keep him from bumping up to the next encounter multiplier. Just be sure to spread them out plenty to avoid getting an area of effect spell or effect dropped on them all at once.

The other option that makes sense fluff-wise, are rutterkin, but with only marginally better attacks and saving throws, the 10x experience cost over the wretches makes them a lousy choice. Five of those will cost you another 4,500 encounter experience. Just not worth it.

TL;DR: what kind of monsters should the sibriex surround itself with?

  • Fast monsters. Any monsters that can cross the battlefield quickly (maybe even with flight) and tie up the PC’s while the sibriex gets into position are a good idea.
  • Grappling monsters. Next, any monster that can auto-grapple the PC’s and prevent them from closing the distance to the sibriex (and also screw with their action economy) are also keen choices.
  • More sibriex-like stuff. Why not double down on the weirdness of the sibriex and use monsters that also create “aberrant” terrain? Wink wink, nudge nudge.
  • Cheap monsters with lots of hit points. Remember, you’ve got to get through area effects and stuff like spirit guardians, so these guys need to last at least one turn before they get munched up. Preferably 50-70 hit points, keeping them in CR 1 territory.
  • Demons, undead, etc. Finally, the monsters need to fit the flavor. A sibriex isn’t going to surround itself with unicorns or bugbears.



Here are the monsters I suggest:

  • Abyssal Wretches (Mordenkainen’s Tome of Foes). Fluff-wise, these make the most sense. They have 18 hit points, so they’ll probably survive at least one or two turns. Just don’t clump them up, because all it takes is one good fireball to wipe them out.
  • Darkmantles (Monster Manual). These are another weird, Lovecraftian monster that wouldn’t be totally out of place in the sibriex’s lair. These can catch PC’s by surprise by standing still and looking like stalactites/stalagmites. Then, they can use their darkness aura to get advantage on the attacks and crush the characters. The sibriex has true sight so it can see through the darkness. Finally, darkmantles have 22 hit points, making them tougher than normal, and only cost 100 XP to add to an encounter.
  • Gazers (Volo’s Guide to Monsters). Continuing the Lovecraft theme, it makes sense to throw in some gazers into the sibriex’s lair. Their aggressive action gives them the ability to close distances quickly. Unfortunately, their hit points and AC are kinda shite, so make sure they stay out of range (30+ feet up in the air). They’re kinda dumb, so they’re going to just attack whatever is closest to them and not really be able to size up opponents. But if you’ve got a squad of players who aren’t familiar with these things all they’re going to say is “oh shit, baby beholders!” and try to knock them out first, using up their action economy.
  • Giant Octopi (Monster Manual). This is a weird one, sure, but it’s not tough to reskin some octopi as Lovecraftian horrors that live in the Abyss. Throw in some water hazards in the sibriex’s lair and hide them (they get advantage when doing Stealth underwater), which will give them a bonus on their attack rolls. It’s unlikely melee attackers who rush forward will have high enough Perception rolls to see them. Plus, they’ve got a ton of hit points, which really helps. Oh, and if that’s not enough, they also have freakin’ 15 foot reach on their tentacle attack which auto grapples.
  • Gibbering Mouthers (Monster Manual). A bit more expensive than I’d like them to be (CR 2), they still fit the setting, plus, they have tons of effects that require saving throws which all run on autopilot. Just be sure that they’re all spaced out at least 20 feet apart and not in a line (but still within 120 feet of the sibriex).
  • Star Spawn Grue (Mordenkainen’s Tome of Foes). Here’s another great monster to consider. They’re weird enough to make sense in the setting and have an aura that gives everything that isn’t an aberration disadvantage on attack rolls against non-grue creatures and all saving throws (ha, these things are so “game designer-y”). Again, space them out and have them stay put, just letting their auras do the work while the sibriex uses its magical attacks with advantage. Just make sure that the sibriex (who is a fiend), doesn’t get within their auras himself. Best part? They’re cheap AF at only 50 XP each. You might even consider doing something loopy like having the sibriex suspend them in cages all throughout its lair. Being in a cage and hard to reach (at most 20 feet in the air) means most characters will totally ignore them, plus at 20 feet up, spirit guardians can’t reach (neener neener).
  • Venom Maw (DM Dave). One of my own creations, the venom maw has enough hit points to stand on its own. Plus, it gets advantage on attacks of opportunity. When this feature is combined with its claw/grapple attack, it could tie up PC’s long enough for the sibriex to get into position. Check them out here: Undead Support for Skull Lords.

What should a sibriex’s lair look like?

No matter where the sibriex lives, it should always have at least 120 feet of distance between itself and any entrances to its lair.

Here are the sibriex’s attacks grouped by range:

  • 150 feet: feeblemind
  • 120 feet: dispel magic, Squirt Bile, Warp Creature
  • 90 feet: hold monster
  • 60 feet: command
  • 30 feet: charm person, contamination
  • 15 feet: chain
  • 5 feet: bite

This gives us an idea of how to create the sibriex’s lair. It should have one main entrance (for foot traffic) with a veritable minefield of awful terrain and power-nerfing weenies (star spawn grue) between that entrance and the sibriex. Then, a second entrance, probably up in the ceiling directly above the sibriex so it can make quick getaways if it needs to.

Let’s break it all down:

Entrance (150 feet from the sibriex).

Here is where the PC’s will enter. There’s no way in hell (literally) the sibriex will let the PC’s go any further than 30 feet from here without initiating combat first. Chances are that the sibriex is going to lose initiative so it will use its legendary actions in the meantime. It’s going to be most interested in slowing down fast movers/flyers and those with long range abilities, especially rogues. If it doesn’t look like any of the characters are fast moving, then it will use feeblemind to target spellcasters, especially sorcerors, warlocks, clerics and paladins who won’t be able to make the Intelligence saving throw.

It might be worth it to place a star spawn grue or two in suspended cages (and invisible if possible) above this ring, but spaced out enough to keep them from getting blasted with area-of-effect spells.

First Circle (91 – 120 feet from the sibriex).

The sibriex will want the PC’s to make it this far but go no further as it ultimately wants to use its Warp Creature power on any who dare approach. Therefore, difficult terrain here is a good idea here, too. For monsters, keep it light, since you’ll want the limited monster selection to work mostly as a method to slow creatures down in the next couple rings

Anything that is able to get past this zone quickly (like a paladin on a flying mount), is an automatic target for the sibriex and it will use its Squirt Bile to take it down. It won’t waste Squirt Bile on rogues or monks, knowing they can probably evade the attack. If it’s a creature that could easily mess up its weenies (like spirit guardians), it will use dispel magic to shut down lingering powers, or feeblemind to have it lose concentration (and spellcasting abilities altogether).

If you go the star spawn grue route for back up, they work well in this ring, too.

Second Circle (61 – 90 feet from the sibriex).

Again, this area should try to slow down any who were able to get past the first ring. Hold monster works in this ring, and it’s the perfect attack for most non-divine melee combatants who have lousy Wisdom saves. Remember: hold monster is a concentration-based spell, which means that it can only do this to one character at a time, so it’s going to make it count.


If rogues manage to get this close and the sibriex can’t see it with its passive Perception, here’s where the sibriex will hold an action for it to come out of hiding then immediately lob hold monster at it. Rogues are a massive danger for the sibriex since they can deal incredible damage to the demon and can reasonably avoid feeblemind and Squirt Bile.


This ring should have more monsters to slow characters down, too, and more difficult terrain (preferably one that’s harder to get around like a moat, or jagged terrain). The darkmantles are a good idea here since they can cast darkness that the sibriex can see through, and they can make life hell on PCs. Multiple darkmantles flanking ensures at least a few will hit.

Giant octopi are always a good selection, especially considering their massive reach.

Being so far from the entrance, any lingering auras and powers should have been dispelled at this point. If any remain, the sibriex must dispel those powers here.

Third Circle (31 – 60 feet from the sibriex)

The third ring is still somewhat the same as the second ring. If it wasn’t able to put a halt to any of the tough guys before they got to this point, it now has a new toy to throw at them: command. It will probably use the “flee” command to get them to run back 60+ feet so they can go through the entire barrage again.

If the sibriex has not been able to considerably slow down the characters by this point, (at least 50% of them have made it through the obstacle course) here’s where it should consider escaping upwards to its ceiling exit.

Fourth Circle (16 – 30 feet from the sibriex)

Here’s where things get tough. While Keith thinks the sibriex would be fine with engaging, the truth is that the sibriex only has +6 to hit with its chain.

Charm person won’t work too well thanks to its weakness in affecting hostile creatures. Even with a DC 21, that’s not the kind of risk I think the sibriex would ever take when it’s got way better options for dealing damage in its arsenal.

Here is where its contamination field starts doing its thing. But again, it’s going to have a hard time with Fighters and Barbarians who have strong Con saves that have made it this far. If creatures with great Constitution get this far, the sibriex needs to bail immediately. No way is it going to try its luck with its chain attack or bite against characters designed for melee combat.

I repeat: if a strong melee attacker makes it to the fourth ring, the sibriex will immediately run away.

Close Range (0 – 15 feet from the sibriex)

If the sibriex is caught off guard here, it needs to run away immediately, especially if two or more characters are attacking it. It won’t have enough hit points to survive more than a couple of rounds with attackers in this area, especially if they’ve made Con saves to get past the sibriex’s contamination aura.

The only way I think this would work is if the final ring was over a pit or something difficult to reach the sibriex from, yet it could still hit those on the edges with its chains. Sure, it’d lose its contamination aura’s goodies, but again, when dealing with creatures that get big bonuses to Constitution saving throws, it’s far better off if it just stays out of reach, using held actions and Wisdom-based spells to fend off close attackers.


Hope you liked this!

I think the Sibriex makes an awesome BBEG, especially for 13th-level characters (minus the backup monsters) and 17th-level characters (with the added monsters).

If you have any questions about how the sibriex works, be sure to leave a comment below. Also, read Keith’s article on Sibriex Tactics on his site, The Monsters Know What They’re Doing.

Finally, help out the blog by sharing this post with others.

See you soon.

Art by Wizards of the Coast, myself (Dave Hamrick, and Shutterstock (used with permission).

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