The Slime oozes goo on the board which infects all the pieces it touches. You are initially able to choose what piece you would like the infection to spread from, and the Slime does the rest of the work for you! Any pieces infected will be removed from the board.
This is especially useful when there is a noticeable cluster of pieces you would like to remove, such as special pieces or pieces with a high score legend.
The Slime costs seven blue stars to activate.