Twinning Glass

Cast something, then cast it again for the price of a tap and one mana: a copy engine built entirely around a name-matching restriction. The clause doing the work is "same name as a spell that was cast this turn," which sounds modest until you notice what it demands of your deck. You cannot pair any two spells; you need two literal copies of the same card, fired in the same turn. Pay full mana for the first, then tap and spend one, and the second arrives without its mana cost, so the Glass swaps the second copy's printed cost for a flat one-mana activation. With a burn spell that doubles your reach; with a tutor or a draw spell it gives you a redundancy loop run twice at a steep discount. The timing window is the cleverest part: the activation resolves at instant speed off an already-cast spell, so the free recast can answer at a moment the opponent thought was settled. What keeps it from running away is the deckbuilding tax. The artifact is flat and board-empty, contributing nothing to combat, and the payoff scales only as far as your deck's naming overlap goes; a pile of unique singletons gives it nothing to chew on. The Glass is an idle stone in most decks and a quiet game-ender in one stuffed with twins, and it demands you commit to the second kind as the price of entry.