Cards:Penumbra Wurm  6/6 Trample, When he dies he becomes a 6/6 black.
Set: Apocalypse
Fortitude: Enchant Creature, Sacrifice a land to regenerate enchanted
creature. When Fortitude goes into a graveyard from play, put into
owner's hand. Set: Urza's Saga
    Penumbra Wurm has two lives, right? Well, on his second death, have
a Fortitude attached to him and sacrifice a forest. Regenerate Penumbra
Kavu and he lives! Fortitude goes from graveyard to your hand. Well, I'm
not quite sure if Penumbra Wurm would still be in play or your hand, I
think he'd go to your hand. Either way, you can still play him or
already have him in play. Do this repetitively over and over like the
energizer bunny until you can't do it anymore.
Andrew Gordon