My characters saw these guys splashing around in the acid pools on the security monitors and avoided the room entirely 🙂
DERGHODAEMONS
Large fiend (demodand), neutral evil
Armour Class 18 (natural armour)
Hit Points 162 (18d10 + 72)
Speed 40ft.
STR 18 (+4)Â Â Â Â Â Â Â DEX 17 (+3)Â Â Â Â Â Â CON 18 (+4)
INT 14 (+2)Â Â Â Â Â Â Â WIS 14 (+2)Â Â Â Â Â Â Â CHA 11 (+0)
Saving Throws Dex +7, Con +8, Wis +6, Cha +4
Damage Resistances cold; bludgeon in g, piercing, and slashing from non-magical weapons
Damage Immunities acid, poison
Condition Immunities poisoned
Senses blindsight 120ft., passive Perception 12
Languages Abyssal, Infernal, telepathy 60 ft.
Challenge 12 (8,400 XP)
Feeblemind Aura. By grinding and clicking its mandibles and chitinous plates together (a free action), a derghodaemon can affect all creatures within 30 feet as if by a feeblemind spell (PHB pg. 239).
Daemons are immune to this effect, but all other creatures must make a DC 17 Wisdom save to resist the effects. A creature that makes this save is immune to the effect for 24 hours. A creature that fails remains affected as long as the derghodaemon continues to maintain the aura and the subject remains within 30 feet of the derghodaemon. Once either condition ends, the victim of this effect can attempt a new DC 17 Wisdom save once per minute to recover from the effect; otherwise, it can be cured by a heal, wish, or greater restoration spell. A derghodaemon cannot use its rend attack in any round in which it uses its feeblemind aura. This is a sonic mind-affecting effect.
Magic Resistance. The derghodaemon has advantage on saving throws against spells and other magical effects.
Magic Weapons. The derghodaemon’s weapon attacks are magical.
Swarmwalking. A derghodaemon is immune to damage or distraction effects caused by swarms.
ACTIONSÂ Â Â Â Â Â Â Â Â Â
Multiattack. The derghodaemon makes three attacks. If all three attacks hit the same target it may then make a rending attack.
Claws. Melee Weapon Attack: +8 to hit, reach 5 ft., one target.
Hit: 8 (1d8 + 4) slashing damage. The target must make a DC 17 Constitution saving throw, taking 10 (3d6) poison damage on a failed save, or half as much damage on a successful one.
Rend. The targeted creature is slashed repeatedly and rapidly. The target takes 42 (12d6) slashing damage unless it uses its reaction to enter a fully defensive stance taking only half damage.
Insect Plague (1/Day on a natural 15+). A swarm of biting insects, mostly spiders but also wasps and scorpions, spreads out from the derghodaemon in a 20 foot radius moving with the creature. When the area appears, each creature in it must make a Constitution saving throw. A creature takes 20 (4d10) piercing damage on a failed save, or half as much damage on a successful one. A creature must also make this saving throw when it enters the spell’s area for the first time on a turn or ends its turn there.
Summon Demodand (1/Day). The derghodaemon attempts to summon another of its kind.  The demodand only has a 30 percent chance of success. The summoned demodand appears in an unoccupied space within 60 feet of its summoner, acts as an ally of its summoner, and can’t summon other demons. It remains for 10 minutes, until it or its summoner dies, or until demodand dismisses it as an action.
DESCRIPTIONÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
A deadly and vicious bouquet of insectile claws sprouts from this horrid, three-legged, multi-eyed beast.