Riveting Rigger [Unstable]

When Riveting Rigger enters the battlefield, you may sacrifice another artifact. If you do, put two +1/+1 counters on Riveting Rigger and it assembles a Contraption. (Put the top card of your Contraption deck face up onto one of your sprockets.) “Turn a blender into an arc welder with a portable fusion reactor and a frozen yogurt dispenser? We can do it!”