Multiattack

The whisperer in the darkness makes two Grasp of the Void attacks.

Grasp of the Void

Melee Spell Attack: +12 to hit, reach 5 ft., one target. Hit: 21 (6d6) force damage, and the target must succeed on a DC 18 Constitution saving throw or be stunned 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.