Keen Smell. The hound has advantage on Perception checks that rely on smell.

Innate Spellcasting. The hound's innate spellcasting ability is Wisdom (spell save DC 13). It can cast the following spells innately, requiring no material components:

At will: mind sliver
1/day each: hunter's mark, Bloodletter

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

A Cute Assimilation. The Hound assimilates foreign DNA across the battlefield. If the hound incapacitates a creature that fails a DC 10 Constitution saving throw, it becomes an Assimilate. Assimilates share Beefy's stat block but revive with 1hp and heal 4hp on a landed attack and can also spread A Cute Assimilation. 

Multiattack. The hound makes two attacks: two with its bite or one with its bite and one with its Tentacle

Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: (2d8 + 3) piercing damage plus (1d8) acid damage.

Mantis Tentacle. Melee Grapple Attack: +4 to hit, reach 10 ft. one target. Hit: (2d6 + 3) piercing damage. You can choose to attempt a grapple. Grappled opponents have disadvantage against A Cute Assimilation.

At higher levels: When you cast this spell using a spell slot of 3rd level or higher, you can increase the damage dealt by a festering wound by 1d6 for each slot level above 2nd.