Tread Mill

At the beginning of your upkeep, if you control any Contraptions, move the CRANK! counter to the next sprocket. You may then crank any number of Contraptions on that sprocket, causing their abilities to trigger. Cranking a Contraption is always optional.

If you or a permanent you control are instructed to assemble a Contraption, reveal the top card of your Contraption deck. Put it onto the battlefield on one of the three sprockets.

While Contraptions you control are on the battlefield, the Contraption deck is not, even if you are using it to signify the three sprockets.

If you crank multiple Contraptions, their abilities can be put onto the stack in any order. The ability put onto the stack will resolve first.

Contraptions aren't put into your main deck. They go into a separate deck called the Contraption deck.

Contraptions are artifacts. Anything that interacts with artifacts will interact with Contraptions.

If a Contraption would leave the battlefield and go to any zone other than exile, it instead goes to the scrapyard, the Contraption deck's version of the graveyard. Things that affect the graveyard do not affect the scrapyard. You can exile Contraptions just fine.

If you or a permanent you control assembles a Contraption and your Contraption deck is empty, nothing happens. You don't lose the game.