Ice Over

The artifact clause is the tell. Tap-down auras have existed since the earliest sets, but most speak only to creatures: keep a blocker locked or pin an attacker in place. Extending the ability to artifacts turns this into something stranger than a combat tool. It can freeze a mana rock the moment after its owner has tapped it dry, lock down a key artifact whose value lives in its activated ability, or strand a Vehicle in crewed-but-spent limbo. Against creatures it is a permanent rather than a one-shot, so the lock persists across turns until someone removes the Aura, which is the price of asking it to hold a threat down indefinitely instead of just trading. Its narrowness lies in timing: nothing here taps the target, so the effect only bites something already tapped. Land it on a tapped attacker and it stays tapped, unable to untap and therefore unable to block. But the untapped case is not a whiff so much as a different kind of leverage: to avoid freezing the permanent, the controller has to leave it untapped, which means declining to attack with it or fire its tap ability at all. Either way the threat sits idle, and that soft prison is the whole point. What holds a two-mana effect like this in line is that it neither destroys nor exiles: it merely denies the untap, and a permanent that never needed to tap slips out from under it entirely. The closest structural cousin is Stasis narrowed to a single permanent, trading the table-wide lock for the durability an Aura provides.