Grick

A grick on the party's side is genuinely strange, so commit to the strangeness. Maybe a deep-gnome alchemist has tamed one with regular meals and a chemical compulsion. Maybe a warlock with a Great Old One patron treats a local grick as a familiar by another name. Maybe the party's druid managed Speak with Animals on something that barely qualifies as one and the conversation went somewhere unsettling. Whatever the setup, the grick is not a friend. It is a tool that hasn't decided to eat the wielder yet.

In play, the grick is a tunnel scout and ambush specialist. With climb 30 ft. and darkvision 60 ft. it can crawl along a passageway ceiling ahead of the party, pick a spot, and wait. When the enemy patrol arrives, the grick drops on the rearmost target, hits with Beak and Tentacles, and grapples them away from their friends with a four-tentacle DC 12 escape. That gives the party a free initiative round on a smaller engagement than they would have faced. Use it for goblin patrols, cult raiding parties, anything where one isolated kill changes the math.

The grick will not coordinate. It does not respond to verbal commands beyond simple cues (a flute pitch, a thrown gobbet of meat). It will not fight enemies on the floor if there's a fresher target on the ceiling or behind it. The handler should always be one decision away from being the meal.

Have the grick make one specific noise the party learns to associate with it dropping. The first time they hear it from somewhere they didn't expect, the table goes quiet on its own.

A grick is a ceiling ambush in any tunnel narrow enough that the party can't easily look up. CR 2, 54 HP, AC 14, 30 ft. climb, Stealth +4, passive 12, darkvision 60 ft. Its purpose at the table is to punish parties that march in formation through a corridor and don't think about what's twenty feet above them. Pick the room before you pick the turns: a vertical shaft, a cavern with stalactites, a sewer where the ceiling is just out of torchlight.

Open from above. The grick clings to the roof with Climb 30 ft. and drops on the rear-marcher, which is usually the wizard. Multiattack gives one Beak (+4 to hit, 9 piercing) and one Tentacles (+4 to hit, 7 slashing plus a Grapple from all four tentacles, escape DC 12). The grapple is the encounter. A medium or smaller PC pulled flat in a tunnel separates the party and forces the front line to turn around in five-foot increments while the grick chews. Apply that to the lowest-Athletics, lowest-Acrobatics member, and the rest of the round writes itself.

Damage is mediocre and AC 14 with 54 HP is paper against a serious party, so the grick wins on terrain or it doesn't win at all. Use the climb speed to retreat to the ceiling between turns, force ranged attackers to fire at upward angles into shadow, and disengage into the next chamber if the front line catches up. Gricks fight until killed because they're hungry and not bright (Int 3). A single grick is a cautionary tale; two in the same shaft, one above and one ahead, justifies the CR.

Describe the wet, rasping clatter of beak on rock before you call for the Stealth check. The party should hear the grick miss its first attack on something the night before.