Mjölnir, Storm Hammer

Most equipment measures its payoff in combat math on the bearer: extra power, evasion, a keyword. This one turns the attack step into a control ritual that ignores the bearer's board presence entirely. Every time the equipped creature swings, the defending player loses a creature to a tap-and-stun (a lockdown that costs them a full untap step to break), and then the hammer deals damage to each opponent equal to the number of tapped creatures that opponent controls. The stun counter is the linchpin: because it eats the next untap, the creature you tap this attack is still tapped when the following attack counts the board, so repeated swings keep more creatures caught in the total. Point the equipped creature at a full board and the damage stays high, because each frozen creature lingers a turn before shaking off its counter. The design is a flavor conceit rendered in mechanics: Mjölnir arrives already attached, seeking a worthy wielder among your legends rather than waiting to be picked up, but that legendary requirement lives only in the enter-the-battlefield trigger. Re-equip it by hand and it will bolt onto any creature you like. The steep equip cost is the real guardrail: dropping the hammer once via its own trigger is free, but moving it onto a new body after the first dies asks for a genuine reinvestment. It rewards a battlefield you can keep pointing at the same opponent, turn after turn, watching their side of the board tap down and stay down.