D&D 5E Carrion Crawler Queen lair

[Quickleaf]

The last two actions look like legendaries to me--they're more reactive, and might make the fight seem more dynamic if they happen at unpredictable intervals.

Cool lair actions... hmmm. Some kind of ranged aoe effect seems about right; like maybe an exploding egg pod spreading noxious goo, or a foul stench blowing out of tunnels at intervals spreading choking those caught in it?

Ok, I sat down and tried re-working it a bit with the advice so far, particularly re-working the lair actions:

Carrion Crawler Queen
As per a MM carrion crawler with the following changes:
Size/Type/Alignment Huge aberration unaligned
HP 76 (8d12+24) (a grabbing tentacle has 12 hp)
Enduring Poison. Creatures suffer disadvantage on saving throws against her poison while grabbed by the Queen’s tentacles.
Multiattack. Make eight attacks: five paralyzing tentacles (reach 15 ft.), two grapple attempts (reach 15 ft., can be replaced with pulling an already grappled creature 15 ft.), and one bite. The same creature may not be targeted by more than one paralyzing tentacle.
Threatening Aquatic Reach. The Queen can make up to five opportunity attacks with its paralyzing tentacles. USUALLY these only trigger if a creature moves outside of its 15 ft. tentacle reach. However, for a creature moving thru or into water, they trigger as long as the creature moves away from the Queen, even if it's just 5 or 10 ft. away. Only one opportunity attack may be made per creature.
CR 3 (750 XP)

[SBLOCK=Lair Actions]
On initiative count 20 (losing all initiative ties), the Carrion Crawler Queen can use one of its lair action options. The Queen cannot use the same lair action in consecutive rounds.
Call the Young: The Queen screeches ear-piercingly. Elves and gnomes (and others with sensitive ears) within 30 feet must make a DC 13 Constitution saving throw or be deafened for one minute. 2 swarms of insects (centipedes) burst forth from nearby egg sacks and act on their own initiative count, attacking weak or unconscious creatures. The Queen may call a total of up to 6 swarms.
Erupting Egg Pod: An egg pod in the lair erupts, spewing noxious vapors in a 10 ft. radius; make a DC 13 Constitution saving throw or be poisoned until the end of their next turn. Carrion crawlers and insect swarms preferentially target creatures poisoned in this way.
Hidden in the Pools: The Queen moves up to her speed, and if she reaches a pool of water, she submerges herself and can make a Stealth check with advantage.[/SBLOCK]

[SBLOCK=Regional Effects]
Cairngorm’s Hollow is plagued by the following effects while the Carrion Crawler Queen is alive. If the Queen is killed, the following effects fade over 1d10 days.

• Carrion crawlers infest the waterways, feasting on corpses, carrion, and easy prey.
• Disease affects the livestock and other domesticated animals.
• Corpses left in the open attract carrion crawlers in 1d10 hours and are soon eaten.[/SBLOCK]
  
  [SBLOCK=Treasure]
  MAIN: corpse has a pouch with 120 gp, a dagger, a vial of basic poison, and a poisoner’s kit
  Pool A: Open chest on bottom of pool with 2,400 cp and 900 sp scattered
  Pool B: Arrow +1 imbedded underwater (CALTROPS TRAP), at the end carnelian veins can be tapped for 9 carnelian gems (worth 50 gp each once treated and polished by a gemologist)
  Pool C: Spell scroll (locate object) in a waterproof case at pool’s bottom
  Pool D: Up to 3 doses of carrion crawler venom can be harvested from hatchling crawlers[/SBLOCK]

 

[dd.stevenson]

Looks pretty cool to me. If I was adapting it for my games I'd probably pare down the aquatic reach as I play gridless, and I'd give it fewer attacks with automatic grapples, but those are mostly playstyle things.