Wall of Tanglecord

Six toughness for two generic mana, with the answer to fliers held back behind a green activation rather than baked into the rate: that split moves the color requirement out of deckbuilding and into the moment of use. Any deck can deploy the wall as a colorless ground-stopper, because casting it asks for no green at all; only the reach upgrade wants a green source, and only when a flier actually shows up. The activation is repeatable, so a single green source covers every turn the threat lingers, and against a purely ground-based board the mana stays free for whatever else the turn needs. The 0/6 does the heavy lifting on its own, blunting early aggression without ever trading down, and the reach toggle patches the lone vulnerability a wall that tall would otherwise leave: things in the air. What results is a defensive piece that rewards green without demanding it, the colorless cost letting it sit in manabases that could never reliably support a colored reach blocker while still paying off the decks that can turn the air on at will.