Forja de Aço Negro
Fragua de acero oscuro
Artifacts you control have indestructible. (Effects that say "destroy" don't destroy them. Artifact creatures with indestructible can't be destroyed by damage.)
Because damage remains marked on a creature until the damage is removed as the turn ends, nonlethal damage dealt to an artifact creature you control may become lethal if Darksteel Forge leaves the battlefield during that turn.