Kefnet's Monument

One of a five-piece cycle of legendary artifacts that each paired a color-aligned cost reducer with a creature-cast trigger, and the blue version's rider is the clearest statement of what kind of deck it was built to feed. Shaving a generic mana off every blue creature spell is the accelerant; the rider is what turns volume into pressure. Every creature spell you cast prevents one of an opponent's creatures from untapping during their next untap step, and because the trigger fires once per cast, a turn spent chaining cheap bodies can freeze several of their creatures at once. That is a tempo posture by design: you are not just developing your side, you are sidelining a piece of theirs with each commitment. The constraint that stops it short of a lock lives in timing and targeting. The trigger keys off the cast rather than resolution, so it does nothing against token-makers or effects that bypass the stack, and "doesn't untap" only bites permanents that are already tapped or that the opponent needs available; an untapped creature simply stays free. Being legendary caps the redundancy: one copy at a time, one discount, one rider per cast. The result is a flat-rate engine that means nothing outside a wide, creature-dense blue shell casting bodies turn after turn, and everything inside one.