Cerbulette

Standing Leap. The cerbulette's long jump is up to 30 feet and its high jump is up to 15 feet, with or without a running start.

Reactive Heads. For each head the cerbulette has beyond one, it gets an extra reaction that can be used only for opportunity attacks.

Multiple Heads. The cerbulette has three heads. While it has more than one head, the cerbulette has advantage on Wisdom (Perception) checks and on saving throws against being blinded, charmed, deafened, frightened, stunned, or knocked unconscious.

Whenever the cerbulette takes 65 or more damage in a single turn, one of its heads dies. If all its heads dies, the cerbulette dies.

At the end of its turn, it grows all of its heads back, unless it has taken fire or acid damage since its last turn. The cerbulette regains 25 hit points for each head regrown in this way.

Wakeful. When one of the cerbulette's heads is asleep, the other two are awake. 

Multiattack. The cerbulette makes as many bite attacks as it has heads.

Bite. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 31 (4d12 + 5) piercing damage.

Deadly Leap. If the cerbulette jumps at least 15 feet as part of its movement, it can then use its action to land on its feet in a space that contains one or more other creatures. Each of those creatures must succeed on a DC 20 Strength or Dexterity saving throw (target's choice) or be knocked prone and take 15 (3d6 + 5) bludgeoning damage plus 15 (3d6 + 5) slashing damage. On a successful save, the creature takes only half the damage, isn't knocked prone, and is pushed up to 10 feet out of the cerbulette's space into an unoccupied space of the creature's choice. If no unoccupied space is within range, the creature instead falls prone in the cerbulette's space.