Mana Leech

The clever bit is the soft lock baked into the untap restriction. Tap this 1/1 to tap an opponent's land, and that land can't untap for as long as the leech itself stays tapped: you keep the lock by declining to untap during your own untap step. The card carries its own off-switch, so the prison only holds if you commit the creature to holding it. That trade is the design discipline: you spend a body and the use of a permanent to keep a single enemy land offline indefinitely, but the moment you want the leech back (to block, to attack, to relocate the lock) the trapped land comes online with it. And the lock is strictly one-for-one: to redirect it onto a fresh land you must first untap the leech, which immediately frees whatever it was holding. So the effect lives on a fragile creature rather than an enchantment because that fragility is the cost: a single removal spell or a point of burn unwinds the whole thing and hands the land back, and there is no way to grind a player off multiple sources at once with a single copy. This is incremental land-denial of the patient sort, an attrition piece that punishes slow, color-screwed starts and rewards a board where you can afford to leave a one-power blocker tapped sideways for several turns running.