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 (You descended if a permanent card was put into your graveyard from anywhere.) 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.

(Transforms from Brass's Tunnel-Grinder.) : Add . Whenever you cast a permanent spell using mana produced by Tecutlan, the Searing Rift, discover X (Exile cards from the top of your library until you exile a nonland card with mana value X or less. Cast it without paying its mana cost or put it into your hand. Put the rest on the bottom in a random order.), where X is that spell's mana value.