Armor Class 15 (natural armor)
Hit Points 45 (7d8 + 14)
Speed 50 ft.
Skills Perception +5
Damage Immunities fire
Senses darkvision 60 ft., passive Perception 15
Languages understands Infernal but can't speak it
Challenge 3
Keen Hearing and Smell. The hound has advantage on Wisdom (Perception) checks that rely on hearing or smell.
Pack Tactics. The hound has advantage on an attack roll against a creature if at least one of the hound's allies is within 5 feet of the creature and the ally isn't incapacitated.
Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 7 (1d8 + 3) piercing damage plus 7 (2d6) fire damage.
Fire Breath (Recharge 5–6). The hound exhales fire in a 15-foot cone. Each creature in that area must make a DC 12 Dexterity saving throw, taking 21 (6d6) fire damage on a failed save, or half as much damage on a successful one.
Monster Manual (2014), p. 182