Slimy Kavu

Tapping a creature to turn a land into a Swamp reads like fixing your own mana; what it actually does is sabotage someone else's. The conversion is total rather than additive: the targeted land becomes a Swamp, so it stops producing whatever color it made before. In an era of greedy multicolor manabases straining across three, four, or five colors of pips, that ability had teeth. Tap an opponent's only white source on their upkeep and watch a key spell strand in hand. The body is a plain 2/2 with one activated line, but that line is a tempo and disruption tool aimed squarely at the difficulty of casting gold cards, repeatable every turn at the cost of leaving the creature back from combat. Its precision is also its ceiling. Against a mono-color deck that leans on Swamps already, the Kavu is just a 2/2 beater, since converting a land they don't rely on for a needed color denies them nothing. It represents a sharper, narrower strain of mana denial than the land destruction red usually trades in: not killing a source but redirecting it, a denial effect cheap enough to ride an aggressive curve but only earning its keep when the opponent's own color demands are doing the work for you.