Metalcraft — When Bleak Coven Vampires enters the battlefield, if you control three or more artifacts, target player loses 4 life and you gain 4 life.

Indestructible
Darksteel Juggernaut's power and toughness are each equal to the number of artifacts you control.
Darksteel Juggernaut attacks each combat if able.

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.)

Flying

Trample
Whenever an artifact is put into a graveyard from the battlefield, Molder Beast gets +2/+0 until end of turn.

: Create a 1/1 colorless Myr artifact creature token.
, Tap five untapped Myr you control: Search your library for a Myr creature card, put it onto the battlefield, then shuffle your library.

, Sacrifice Salvage Scout: Return target artifact card from your graveyard to your hand.