Spawner of Saproling Dudes

Reveal Spawner of Saproling Dudes when you draft it and choose a number.
Spawner of Saproling Dudes costs {x} more to cast, where {x} is the number you chose.
At the beginning of you upkeep, put the top X cards of your library into your graveyard, and put X 1/1 green Saproling Dude creature tokens into play, where X is the number you chose.