Cerberus

Keen Hearing and Smell. The Cerberus has advantage on Wisdom (Perception) checks that rely on hearing or smell.

Pack Tactics. The Cerberus 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.

Heated Body. A creature that hits it with a melee attack while within 5 feet of it takes 7 (2d6) fire damage.

Multiattack. The Cerberus makes three attacks: three with it's bites.

Bite 1. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 7 (3d8 + 6) piercing damage plus 7 (2d10) fire damage.

Bite 2. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 7 (3d8 + 6) piercing damage plus 7 (2d10) lightning damage.

Bite 2. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 7 (3d8 + 6) piercing damage plus 7 (2d10) necrotic damage.

Bite Down. Melee Weapon Attack: +10 to hit, reach 5 ft., one Large or smaller creature. Hit: 17 (2d10 + 6) piercing damage plus 17 (2d10 + 6) slashing damage. The target is grappled (escape DC 16) if the Cerberus isn't already biting down on a creature, and the target is restrained until this grapple ends.

Swallow. The Cerberus makes one bite attack against a small or smaller target it is grappling. If the attack hits, the target is also swallowed, and the grapple ends. While swallowed, the target is blinded and restrained, it has total cover against attacks and other effects outside the Cerberus, and it takes 21 (6d6) acid damage at the start of each of the Cerberus's turns. A Cerberus can have only one creature swallowed at a time.

Fire Breath (Recharge 5–6). The Cerberus exhales fire in a 15-foot cone. Each creature in that area must make a DC 16 Dexterity saving throw, taking 42 (6d10) fire damage on a failed save, or half as much damage on a successful one.

Lightning Breath (Recharge 5–6). The Cerberus exhales lightning in an 60-foot line that is 5 feet wide. Each creature in that line must make a DC 16 Dexterity saving throw, taking 55 (10d10) lightning damage on a failed save, or half as much damage on a successful one.

Hades Breath (Recharge 5–6). The Cerberus exhales shadowy fire in a 30-foot cone. Each creature in that area must make a DC 16 Dexterity saving throw, taking 56 (16d6) necrotic damage on a failed save, or half as much damage on a successful one. A humanoid reduced to 0 hit points by this damage dies, and an undead shadow rises from its corpse and acts immediately after the dragon in the initiative count. The shadow is under the Cerberus’s control.