Multiattack. The decapus makes two attacks: one with its bite and one with its tentacles.
Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one creature grappled by the decapus. Hit:7 (2d4 + 2) piercing damage.
Tentacles. Melee Weapon Attack: +4 to hit, reach 10 ft., one target. Hit:24 (9d4 + 2) bludgeoning damage or 14 (5d4 + 2) bludgeoning damage if the decapus is grappling a creature other than the target or if the decapus is on the ground or floor. The target is also grappled (escape DC 14) unless the decapus is already grappling a creature. Until this grapple ends, the target is restrained.
Decapuses are carnivorous, solitary hunters that swing through trees, scooping up prey with their 10-foot-long, suckered tentacles. Decapuses also use their tentacles to climb walls and ceilings.