Slayer

Medium Fiend, host's alignment

AC: 19

Initiative: +4 (14)

HP: 136 (16d8 + 64)

Speed: 40 ft.

STR
20 (+5)
DEX
19 (+4)
CON
18 (+4)
INT
13 (+1)
WIS
14 (+2)
CHA
14 (+2)

Saving Throws: Dex +8, Int +5

Skills: Acrobatics +8, Deception +6, Perception +6, Stealth +12

Resistances: bludgeoning, piercing, slashing from nonmagical attacks that aren't silvered

Immunities: poison

Senses: Passive Perception 16

Languages: Languages of the host

CR: 12 (XP 8,400; PB +4)

Assassinate.

During its first turn, the Slayer has advantage on attack rolls against any creature that hasn't taken a turn. Any hit the Slayer scores against a surprised creature is a critical hit.

Devil's Sight.

Magical darkness doesn't impede the Slayer's darkvision.

Magic Resistance.

The Slayer has advantage on saving throws against spells and other magical effects.

Actions

Multiattack.

The Slayer makes four Claw attacks.

Claw.

Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 12 (2d6 + 5) slashing damage plus 7 (2d6) poison damage. The Slayer deals an extra 14 (4d6) slashing damage when it has advantage on the attack roll and hits the target.

Find this creature in the encounter builder

Slayer

Source: Chains of Asmodeus, p. 30 - Licenses and attribution