Shrek, The Swamp Master

Whenever a Swamp enters the battlefield
under your opponents control, you may pay {b/g}{b/g}. If you do, take control of that Swamp.
{p/b}{p/g}: Create an Onion token.
(It's an artifact with "{t}, Sacrifice this artifact: Regenerate target Ogre.")
At the beginning of your upkeep, if you control
five or more Onions and ten or more Swamps,
you win the game.