Shimmer

Pick any land type on the way in, and every land of that type vanishes and returns on its controller's untap step, indefinitely, until someone deals with the enchantment itself. Phasing was Mirage's clean answer to the rules baggage of "destroy" and "exile": a permanent that phases out counts as nonexistent while it's gone, then comes back exactly as it left, untouched by anything that happened in the interim. Here that disappearing act stops being a one-shot trick and becomes a standing rule applied to an entire land type at once. The asymmetry is where it gets interesting: nothing in the text restricts the chosen type to lands you control. Name your opponent's dominant basic and you have a soft, repeating mana denial that strips their resources every other turn while leaving yours alone if you point it at a type you don't run. The friction is the timing. Phasing happens during the controller's own untap step, so an affected land cycles out and back on that player's schedule, not yours, which makes the denial rhythmic rather than absolute. This is a mechanic-first card from an era that built whole sets around a single keyword: a designer's proof of concept that takes the cleverest of Mirage's tricks and asks what an entire color of land looks like when it never quite stays on the battlefield.