Reality Acid

A delayed-fuse Oblivion Ring, with the timer baked into the card rather than left to your opponent. Vanishing turns the Aura into a clock: it lands on any permanent, sits for three of your upkeeps removing a counter each turn, and then sacrifices itself, which triggers the leaves-the-battlefield clause and forces the enchanted permanent's controller to sacrifice it too. The elegance is that it answers things color-blue normally cannot touch (creatures, artifacts, lands, even other enchantments and planeswalkers) by routing the kill through a sacrifice the controller performs, which sidesteps protection, indestructibility, and most regeneration. The cost of that universality is patience: three turns is a long telegraph, and the opponent gets a full window to use, sacrifice, or move the doomed permanent before the fuse burns down. That tension is also where the card's real interest lives. Because removing the Aura is what fires the sacrifice, bouncing or blinking your own Reality Acid resets nothing for the opponent and triggers it immediately, collapsing the three-turn delay into an instant answer the moment you have a way to pick the Aura back up. The same is true if anything destroys it. Build around that interaction and a slow, fair-looking enchantment becomes a repeatable, color-agnostic edict that ignores the usual defenses, which is a far sharper tool than the upkeep-counter text suggests on its own.