Mjölnir, Hammer of Thor

Equip worthy is the whole conceit made mechanical: this Equipment carries no ordinary equip cost, only the worthy gate, which restricts what its equip ability can lawfully target. The wielder chosen by that ability must be a legendary non-Villain that is red and/or white, so if none of your creatures qualify you cannot equip it up in the usual way, and the hammer sits idle. That restriction does double duty. It flavors the object (only the worthy lift it) and it disciplines a payoff that would otherwise warp any deck it touched, because doubling all damage an equipped creature deals is not an effect anyone hands out unconditionally. Damage-doublers are familiar in red, but they usually live on a permanent that does nothing else; here the doubler rides an artifact that also arrives with a four-damage bolt at a creature, folding targeted removal and a static payoff into one legendary object. The doubling is deliberately broad: it reads "all damage," not combat damage, so it compounds fight effects, pings, and damage-based triggers, not merely attacks. There is also a one-time escape hatch, a two-damage sweep of every creature bought by discarding the card from hand, so even a grip full of unworthy creatures can wring a small wrath out of it rather than leaving the hammer stranded. The design gates the ungatable: an effect with no business being cheap rides a body-check only the intended legends can pass.