Multiattack

In fiend form, the infernal swarm makes three attacks: two with its scimitar and one with its slam, or three with its scimitar. In shapeless form, it makes three attacks with its bites.

Bites (Shapeless Form Only)

Melee Weapon Attack: +9 to hit, reach 0 ft., one target in the swarm's space. Hit: 28 (8d6) piercing damage, or 14 (4d6) piercing damage if the swarm has half its hp or fewer.

Poisonous Barb

Ranged Weapon Attack: +8 to hit, range 30/120 ft., one target. Hit: 10 (2d6 + 3) piercing damage, and the target must make a DC 17 Constitution saving throw, taking 18 (4d8) poison damage on a failed save, or half as much damage on a successful one.

Scimitar (Fiend Form Only)

Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 14 (3d6 + 4) slashing damage.

Slam (Fiend Form Only)

Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 18 (4d6 + 4) bludgeoning damage, and the target is grappled (escape DC 17). Until this grapple ends, the target is restrained, and the infernal swarm can't slam another target. In addition, at the start of each of the target's turns, the target takes 14 (4d6) piercing damage.