Sludge Strider 
Artifact Creature — Insect
Whenever another artifact you control enters or leaves the battlefield, you may pay . If you do, target player loses 1 life and you gain 1 life.
Legality
standardNOT LEGALpioneerNOT LEGALmodernLEGALlegacyLEGALvintageLEGALcommanderLEGAL