Mystical Tether

White's O-Ring lineage bought its power at a fixed price: sorcery speed. Oblivion Ring, Banishing Light, and their kin exile at will, but only on your own turn, which means a creature landing on the opponent's turn resolves its trigger, swings, and connects before white gets a chance to respond. This design buys its way out of that constraint without giving it away for free. The base cost keeps it a proactive removal enchantment, but a two-mana surcharge unlocks a flash window, letting it snap onto a fresh threat before combat or catch a game-ending artifact the turn it arrives. That optionality carries the card: it can be both the tempo-neutral maindeck answer you cast on curve and the reactive trump you hold up when you need instant-speed interaction, at a premium you only pay when the moment demands it. The exile-until-leaves clause carries the usual downside of the archetype (kill or bounce the enchantment and the exiled permanent returns), so the flash mode is not a clean removal spell so much as a timing pressure valve, spending extra mana to relocate white's removal into a window it historically could not reach.