Stone Camouflage. The tentacle terror has advantage on Dexterity (Stealth) checks made while in an undertaker location (including a dungeon).
Tentacles. Melee Weapon Attack: +5 to hit, reach 15 ft., one target. Hit: 10 2d6+3 necrotic damage, and the target is grappled (escape DC 16). Until this grapple ends, the octopus can't use its tentacles on another target. Alternatively, the tentacle terror can choose to knock back a target of Medium or smaller size instead of grappling. The target is knocked back 15 feet and knocked prone on a failed DC 15 STR saving throw.