"Did it have this shape upon Mirrodin's creation, or did some inconceivable force shape the unshapable?"
—Pontifex, elder researcher

Darksteel Forge

Artifacts you control have indestructible. (Effects that say "destroy" don't destroy them. Artifact creatures with indestructible can't be destroyed by damage.)

"It is as if this world has been expecting our blessings."
—Elesh Norn, Grand Cenobite

Double Masters

Artifacts you control have indestructible.

Magic 2014

Planechase

Artifacts you control are indestructible. (Effects that say "destroy" don't destroy them. Indestructible creatures can't be destroyed by damage.)

Darksteel

Artifacts you control are indestructible. ("Destroy" effects and lethal damage don't destroy them.)

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.