Brass's Tunnel-Grinder

When Brass's Tunnel−Grinder enters the battlefield, discard any number of cards, then draw that many cards plus one.

At the beginning of your end step, if you descended this turn, put a bore counter on Brass's Tunnel−Grinder. Then if there are three or more bore counters on it, remove those counters and transform it. (You descended if a permanent card was put into your graveyard from anywhere.)