Celestial Hounds

Shapechanger. The Celestial Hound can use its action to polymorph into a beast form that resembles a mastif or a wolf, or back into its tru form. Its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Keen Hearing and smell. The Celestial Hound has advantage on Wisdom (Perception) checks that rely on hearing and smell.

Multiattack. In beast form, the Celestial hound makes two bite attacks. In celestial form, it makes two attacks, only one of which can be with its greatsword.

Bite. Melee Weapon Attack: +5 to hit, reach 5ft., one target. Hit: 6 (1d6 + 3) piercing damage. If the target is a creature, it must succeed on a DC 13 Strength saving throw or be knocked prone.

Greatsword. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 10 (2d6 +3) Slashing damage.