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.)
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(Transforms from Brass's Tunnel-Grinder.) : Add . Whenever you cast a permanent spell using mana produced by Tecutlan, the Searing Rift, discover X, where X is that spell's mana value.