Barghest Assassin

Shapechanger. The barghest assassin can use its action to polymorph into a Small goblin or back into its true form. Other than its size and speed, its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. The barghest assassin reverts to its true form if it dies.

Fire Banishment. When the barghest assassin starts its turn engulfed in flames that are at least 10 feet high or wide, it must succeed on a DC 15 Charisma saving throw or be instantly banished to Gehenna. Instantaneous bursts of flame (such as a red dragon's breath or a fireball spell) don't have this effect on the barghest assassin.

Keen Smell. The barghest assassin has advantage on Wisdom (Perception) checks that rely on smell.

Innate Spellcasting. The barghest assassin's innate spellcasting ability is Charisma (spell save DC 12). The barghest assassin can innately cast the following spells, requiring no material components:

At will: levitate, minor illusion, pass without trace
1/day each: charm person, dimension door, suggestion

Sneak Attack. Once per turn, you can deal an extra 2d6 damage to one creature you hit with an attack with a finesse or ranged weapon if you have advantage on the attack roll. You don’t need advantage on the attack roll if another enemy of the target is within 5 ft. of it, that enemy isn’t incapacitated, and you don’t have disadvantage on the attack roll.

Cunning Action. You can take a bonus action on each of your turns to take the Dash, Disengage, or Hide action.

Bite. Melee Weapon Attack (true form only): +7 to hit, reach 5 ft., one target. Hit: 13 (2d8 + 4) piercing damage.

Claws. Melee Weapon Attack. +7 to hit, reach 5 ft., one target. Hit: 8 (1d8 + 4) slashing damage.

While in Goblin Form:

Dagger. Melee Weapon Attack: +7 to hit, reach 5ft., one target. Hit.  6 (1d4+4) piercing damage.
Dagger. Ranged Weapon Attack: +7 to hit, reach 20(60) ft., one target. Hit. 6(1d4+4) piercing damage.

Shortbow. Ranged Weapon Attack: +7 to hit, reach 80(320) ft., one target. Hit. 8 (1d6+5) piercing damage.