Glimmerdust Nap

The enchant clause is the whole gambit: this Aura can only attach to a creature already tapped, which means it never works as a clean answer the way an untap-locker on any target would. The card stays stuck in hand until a legal target exists; you cannot even try to attach it to an untapped body. The creature has to commit first, by attacking or paying into a tap ability, and only on your following main phase, at sorcery speed, can you strand it sideways. That sequencing makes it a tempo and combat tool rather than removal: you cannot interrupt anything in the moment, only punish a body that already committed and survived to your turn still tapped. The payoff for that patience is permanence. Unlike the older "doesn't untap unless you pay" Auras that levy a recurring upkeep tax, this one costs nothing per turn once it sticks, parking the creature for as long as the enchantment stays attached. It cannot touch anything sitting back on defense, and a blink effect peels it off entirely, returning the creature untapped and ready. As a flavor of pacifism it occupies a distinct corner of blue's toolkit, the color that prefers to neutralize a creature's function rather than kill it, and locking a spent attacker is a tidier expression of that idea than bouncing it ever was. Catch the right tapped body and you have quietly subtracted it from the board for good.