Charnel Hound

Aversion to Sunlight. If exposed to sunlight, the Charnel Hound makes all attack rolls, saving throws, and skill checks with disadvantage.

Body Integration. Whenever the Charnel Hound reduces a humanoid creature, of Large or smaller size, to zero hit points the creature must make a DC 19 Constitution saving throw. On a failed save, the creature's body is absorbed into the Charnel Hound's body, healing it 3 times the Hit Dice of the absorbed creature. An absorbed creature is blinded and restrained, it has total cover against attacks and other effects outside the Hound.

Creatures absorbed by the Charnel Hound have disadvantage on Death saving throws. When a creature dies while absorbed, its body is grafted onto the hound and the Charnel Hound's hit points increase by 10 (healing that amount as well) for 24 hours. After 24 hours, the body is permanently merged with the hound and unrecoverable. Magical items are shunted out of the hound's body, destroying all other non-magical equipment.  

A conscious creature may attempt to break free by using its action and succeeding a DC 19 Athletics check. Large creatures have advantage on this check.

Grave Bound. When the Charnel Hound is reduced to half its hit points or less, rounded down, the its claws and fangs grow in size and become more vicious. The roiling bodies within its form, writhe and scream releasing more toxins into the air. The Charnel Hound's bite and claw attacks deal an additional 2d6 Necrotic damage. Additionally, the range of the Charnel Hound's Putrid Aura increases to 15 feet.

Magic Resistance. The Charnel Hound has advantage on saving throws against spells and other magical effects. 

Putrid Aura. The smell of death and decomposition clings the Charnel Hound within a 5 foot radius. Whenever a creature enters the area for the first time on a turn or starts its turn there, the vomit inducing stench forces the creature to make a DC 19 Constitution saving throw. It takes 2d10 poison damage and is poisoned for 1 minute on a failed save, or half as much damage and isn't poisoned on a successful one. A poisoned creature may make a DC 19 Constitution saving throw at the end of its turn. On a success, the creature is no longer poisoned.

Soul Rend. The Charnel Hound deals an additional 1d8 Necrotic damage with its bite and claw attacks for each creature it has currently absorbed. 

Turn Resistance. The Charnel Hound has advantage on saving throws against any effect that turns undead.

Multiattack. It then makes three attacks: one with its bite and two with its claws. It can substitute its Nightmarish Presence instead of two claw attacks.

Bite. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 18 (2d10 + 6) piercing damage plus 7 (2d6) Necrotic damage.

Claw. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 12 (2d6 + 6) slashing damage plus 7 (2d6) Necrotic damage.

Nightmarish Presence (Recharge 5-6). Each creature of the hound's choice within 60 feet of the hound that can see or hear it must succeed a DC 19 Wisdom saving throw or take 6d6 psychic damage and become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the hound's Nightmarish Presence for the next 24 hours. A creature who is frightened by the hound has disadvantage on subsequent saving throws against this ability.