Create X X/X green Ooze creature tokens.
For example, if you choose for X to be 1, you pay {2}{G} and create one 1/1 Ooze. If X is 2, you pay {4}{G} and create two 2/2 Oozes. If X is 3, {6}{G} gets you three 3/3 Oozes, and so on.