Multiattack

The bone swarm can attack every hostile creature in its space with swirling bones.

Swirling Bones

Melee Weapon Attack: +10 to hit, reach 0 ft., one creature in the swarm's space. Hit: 31 (5d8 + 9) bludgeoning, piercing, or slashing damage (includes Strength of Bone special ability).

Death's Embrace (Recharge 5-6)

Melee Weapon Attack: +10 to hit, reach 0 ft., one creature in the swarm's space. Hit: the target is grappled (escape DC 16) and enveloped within the swarm's bones. The swarm can force the creature to move at its normal speed wherever the bone swarm wishes. Any non-area attack against the bone swarm has a 50 percent chance of hitting a creature grappled in Death's Embrace instead.