Magical Immunity. The Slasher has a magical shell that makes it immune to force damage, and has a 50 percent change of reverberating back at the caster.

Burrowing Sneak Attack. Once per 2-3 rounds the Slasher can make a burrowing sneak attack, giving them surprise and giving them and extra 2 damage dice on their attack.

Multiattack. Slashers make

Pounding Slash Melee Weapon Attack: +8 to hit, reach 10 ft., 1 target. Hit: 20 (5d6 + 5) slashing damage. 

Blinding Flash. Reach 50 ft. radius, everyone in a 50 ft. radius must succeed on a DC 17 Constitution saving throw or become blinded for two rounds, while blinded the Slasher makes an opportunity attack on you for half damage.

Grappling Strike. Melee Weapon Attack: +8 to hit, range 30 ft., 1 target. Hit: 11 (2d6 +5), the target must succeed on a DC 17 Strength saving throw or become restrained.

Charging Bash. Melee Weapon Attack: +8 to hit, range 30 ft., 1 target. Hit: 18 (3d8 + 5) bludgeoning damage, plus 9 (1d6 +5) piercing damage.