Belch Hound, Swamp of Oblivion

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.

Blight Pox. The hound transmits a disease to any creature that encounters it, after every encounter one must pass a DC 15 Con save or contract the disease, Lose 1d6 cha per day, at zero cha the player dies and becomes a new belch hound.

Bite. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 7 (1d8 + 3) piercing damage plus 7 (2d6) poison damage.

Belch (Recharge 5–6). The hound exhales acid in a 15-foot cone. Each creature in that area must make a DC 12 Dexterity saving throw, taking 21 (6d6) acid damage on a failed save, or half as much damage on a successful one.