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.