Baneling

Creep Affinity. While on ground covered with creep, the baneling's speed is doubled and it can burrow and unburrow as a bonus action.

Caustic Rupture. As an action the baneling can cause its volatile internal fluids destroying itself and coating nearby creatures in its acidic guts. Any creature within 10 ft of a baneling that uses its Caustic Rupture must make a Dexterity Saving Throw (DC 15) or take 11 (2d10) Acid damage and half as much at the start of their next turn. A creature that succeeds on saving throw takes half damage and does not take the additional damage.

Burrow. As an action, the baneling can burrow beneath the ground. While burrowed in this way the baneling is undetectable to a creature without tremor sense. A DC 15 Intelligence Investigation can reveal the disturbed earth. A burrowed baneling can unburrow as an action or using it's Ambush reaction.

Enhanced Adrenal Glands. The baneling can take the dash action as a bonus action.

Ambush. When a burrowed baneling senses a creature within 10 ft. of it it may use its reaction to burst from the ground and leap at the creature and use its Caustic Rupture ability.