Aplan Mortarium

Planechase runs on the chaos of the planar die, but this plane weaponizes the one certainty the format offers: your own upkeep. The Byzantium Radiation trigger fires at the start of each of your turns regardless of what the die shows, stacking exposure counters that convert directly into escalating life loss. It is a countdown that never resets while you hold the plane, which turns the ordinary Planechase impulse (roll to move on, roll for chaos) into a decision under duress. The plane rewards you for staying: chaos yields two 2/2 first-strike, vigilant bodies that briefly stop being creatures whenever an opponent casts a creature spell, slipping out of creature-targeted removal at the exact moment an opponent commits to the board. That conditional non-creature clause is the clever half of the design, a defensive window keyed to the opponent's tempo rather than your own; the tokens are not evasive attackers, they are durable ones, first strike punishing blocks and vigilance keeping them home to hold the plane. What makes the design cohere is the two abilities pulling in opposite directions: one bleeds you out on a fixed schedule, the other rewards you for staying long enough to accrue an army. Planeswalking away costs you nothing already built (the tokens stay under your control), so the real tension is whether the next exposure tick is worth another roll at chaos. The plane raises the price of patience every turn, then dangles a resilient reinforcement to make patience worth it.