Darksteel Sentinel

Darksteel Sentinel

Artifact Creature - Golem | Power/Toughness: 3 / 3 (CMC 6)
Flash (You may cast this spell any time you could cast an instant.)
Vigilance
Indestructible (Damage and effects that say "destroy" don't destroy this creature. If its toughness is 0 or less, it's still put into its owner's graveyard.)