Chilling Touch

Melee Weapon Attack: +5 to hit, reach 0 ft., one creature in the swarm's space. Hit: 28 (8d6) cold damage, or 14 (4d6) cold damage if the swarm has half of its hp or fewer. The target must succeed on a DC 13 Constitution saving throw or be unable to regain hp for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.