Slime Pearl:

A science experiment gone right, this is the last artifact of Bunus Underfist.

Gelatinous Cube:

As an Action, throw this at a creature you can see.

If the Creature is more than 30ft. away they have advantage on the saving throw. 

The creature must make a DC 20 Dexterity save or become engulfed as the Pearl explodes in oozing fury, summoning a temporary Huge ooze around the creature. If the Creature is bigger than Huge, they take half damage.

After summoning, the Ooze will attempt to reconstruct itself for the next 10 turns, after which it will dissolve.

Engulf.

On a successful save, the creature can choose to be pushed 5 feet back or to the side of the cube. A creature that chooses not to be pushed suffers the consequences of a failed saving throw.

On a failed save, the cube enters the creature's space, and the creature takes 21 (6d6) acid damage and is engulfed. The engulfed creature can't breathe, is restrained, and takes 21 (6d6) acid damage at the start of each of the cube's turns. When the cube moves, the engulfed creature moves with it.

An engulfed creature can try to escape by taking an action to make a DC 19 Strength check. On a success, the creature escapes and enters a space of its choice within 5 feet of the cube.