Mishra's Groundbreaker 
Artifact
, Sacrifice this artifact: Target land becomes a 3/3 artifact creature that's still a land. (This effect lasts indefinitely.)
Legality
standardNOT LEGALpioneerNOT LEGALmodernNOT LEGALlegacyLEGALvintageLEGALcommanderLEGAL