Grafted Exoskeleton

Flying You can't lose the game and your opponents can't win the game.

Defender (This creature can't attack.)

Metalcraft — This creature gets +2/+2 as long as you control three or more artifacts.

Metalcraft — T: Tap target artifact, creature, or land. Activate only if you control three or more artifacts.

T: Add W.

When this creature dies, return another target artifact card from your graveyard to your hand.

T: Add U.