Armor Class 16 (natural armor)
Hit Points 90 (12d10 + 24)
Speed 40 ft.
Skills Perception +8
Damage Resistances cold, fire, lightning, [object Object]
Condition Immunities frightened
Senses darkvision 60 ft., passive Perception 15
Languages understands Abyssal but can't speak
Challenge 8
Pack Tactics. A howler has advantage on attack rolls against a creature if at least one of the howler's allies is within 5 feet of the creature and the ally isn't incapacitated.
Multiattack. The howler makes two bite attacks.
Rending Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) piercing damage. If the target is frightened it takes an additional 22 (4d10) psychic damage. This attack ignores damage resistance.
Mind-Breaking Howl (Recharge 5–6). The howler emits a keening howl in a 60-foot cone. Each creature in that area that isn't deafened must succeed on a DC 16 Wisdom saving throw or be frightened until the end of the howler's next turn. While a creature is frightened in this way, its speed is halved, and it is incapacitated. A target that successfully saves is immune to the Mind-Breaking Howl of all howlers for the next 24 hours.
Mordenkainen's Tome of Foes, p. 210