Darksteel Reactor

Indestructible (Effects that say "destroy" don't destroy this artifact.)
At the beginning of your upkeep, you may put a charge counter on this artifact.
When this artifact has twenty or more charge counters on it, you win the game.

Historic Anthology 1

Indestructible
At the beginning of your upkeep, you may put a charge counter on Darksteel Reactor.
When Darksteel Reactor has twenty or more charge counters on it, you win the game.

Darksteel

Darksteel Reactor is indestructible. ("Destroy" effects and lethal damage don't destroy it.)
At the beginning of your upkeep, you may put a charge counter on Darksteel Reactor.
When Darksteel Reactor has twenty or more charge counters on it, you win the game.