Swarm. The swarm can occupy another creature's space and vice-versa, and the swarm can move through any opening large enough for a small voidling. The swarm can't regain hit points or gain temporary hit points.   Pack Tactics. The voidling has advantage on an attack roll against a creature if at least one of the voidling's allies is within 5 feet of that creature and the ally isn't incapacitated.   Rupture. The voidling explodes on death, dealing 1d6 acid damage to all adjacent creatures (except other voidlings or the Mother) with no save allowed.