Mishra's Self-Replicator 
Artifact Creature — Assembly-Worker
Whenever you cast a historic spell, you may pay . If you do, create a token that's a copy of this creature. (Artifacts, legendaries, and Sagas are historic.)
Legality
standardNOT LEGALpioneerLEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL