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 hit points or fewer. The target must make a successful DC 13 Constitution saving throw or be unable to regain hit points. An affected creature repeats the saving throw at the end of its turns, ending the effect on itself with a successful save. The effect can also be ended with a greater restoration spell or comparable magic.