Cerberus Puppy

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.

Cerberus's Curse. Whenever Cerberus hits a creature with its bite attack, that creature is forced to remain in its current plane until the curse is removed by the remove curse spell or other magic.

Multiple Heads. The Cerberus has three heads. While it has more than one head, the Cerberus has advantage on saving throws against being blinded, charmed, deafened, frightened, stunned, and knocked unconscious.

Whenever the Cerberus takes 27 or more damage in a single turn, one of its heads dies. If all its heads die, the Cerberus dies.

Relentless Tracker. The Cerberus knows the distance to and direction of any creature under the effect of its curse, as long as the creature and the Cerberus are on the same plane of existence. If the creature being tracked by the Cerberus dies, the Cerberus knows.

Soul Scent. The Cerberus can pinpoint, by scent, the location of any soul within 30 feet of it.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 5 (1d4 + 3) piercing damage plus 7 (2d6) fire damage.

Multiattack. The Cerberus makes as many bite attacks as it has heads.

Fire Ray. Range Spell Attack: +5 to hit, range 30/90 ft., one target. Hit: 10 (3d6) 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.