Boggart

Don't Call Its Name. The Boggart should never be called by its name or associated name, for when its name is called it cannot be reasoned with, placated or controlled.

Frenzy. Once the boggart is at half hp, it goes into a frenzy and has Advantage on its melee attacks against a creature and can use Devour as a bonus action (if successful to recharge), other creatures have Advantage to hit the boggart due to its reckless and wild attacks.

Evasion: Even though the Boggart isn't perceptive, its senses heighten when making a Dexterity Save against certain area effect attacks such as fireball or Blue Dragons Lightning Breath. It takes no damage if it succeeds the save or Half damage on a failed save.

Leap: The boggart can leap up to 20ft with or without a running start to close the gap between itself and its prey.

Multiattack. (Boggart Form Only). The boggart makes three attacks, two with its claws and one kick.

Unarmed Strike (Boggart Form Only). Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 7 (1d8 + 4) slashing damage. 

Kick (Boggart Form Only). Melee Weapon Attack: +7  to hit, reach 5ft., one creature. hit:7 (1d10+4) bludgeoning damage

Bite. (Boggart Form Only). Melee Weapon Attack: +7 to hit, reach 5 ft., a creature that is Knocked prone by the boggart. Hit: 7 (2d6 + 4) piercing damage

Devour (Recharge 5-6): The Boggart leaps on a creature within 30ft on a failed Strength save (15) the creature is knocked prone and the boggart tears into the creature dealing (2d6+4 piercing damage) plus being able to temporarily heal the boggart for half the damage it dealt to a creature.

Deflect Missiles. The Boggart uses its Reaction to deflect or catch the missile when its  hit by a ranged weapon Attack. When it does so, the damage it takes from the Attack is reduced by 1d 10 + its Dexterity modifier + creature level. If it reduces the damage to 0, it can catch the missile if it is small enough for it to hold in one hand and have at least one hand free, the Boggart will slam it into the nearest creature within 5ft dealing (the Ammunition damage) 

Spring into action.  Once attacked by a ranged attack, this creature can disengage and charge at full speed to the creature it was attacked by.