Crystaloid Reaper

Aggressive. As a bonus action, the reaper can move up to its speed toward a hostile creature that it can see.

Aversion of Necrotic. If the reaper takes necrotic damage, it has disadvantage on attack rolls and ability checks until the end of its next turn.

Magic Weapons. The reaper's weapon attacks are magical.

Unity. The reaper has advantage on an attack roll against a creature if at least one of the reaper's allies is within 5 ft. of the creature and the ally isn't incapacitated.

Slam. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: (2d6 + 3) bludgeoning damage. If the target is a creature, it must succeed on a DC 13 Strength saving throw or be knocked prone