Shreech (5e Creature)
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Medium monstrosity, unaligned
Claw. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 15 (3d8 + 2) slashing damage.
Vocal Blast. One creature within 30 ft. that the shreech can see must succeed on a DC 15 Constitution save, taking 30 (8d6 + 2) thunder damage and being stunned for 1 round on a failed save, or taking half as much damage and becoming deafened for 1 round on a success; if the target is within 10 ft., it makes this save with disadvantage. Additionally, all other creatures within 10 ft. of the shreech take 8 (2d6 + 1) thunder damage and must succeed on a DC 12 Constitution save or be deafened for 1 round.
Backup Singer. If a creature within 10 feet of the shreech deals thunder damage to another creature, the shreech can amplify the sound and cause the target to take an additional 8 (2d6 + 1) thunder damage.
A sinuous and agile monster, the schreech feeds mainly on algal biofilm and insects but is fond of harassing and startling unsuspecting creatures using its deafening, agonizing wail. Most of its body is adapted to generate vibration and emit sound from its mouth, eye sockets, ears and nostrils, all functioning as additional vocal pipes and sonar pits. It floats through the air like an eel, but employs its clawed tail to anchor itself in place and can retract to a squat stump or stretch into a sinuous ribbon to feed.
Often found accompanied by one or more of these creatures, the Shreeg is sometimes theorized to represent an "adult" form of the shreech, which would in turn be comparable to a larva.