Lurking Green Dragon

The attack restriction is the whole engineering problem here, and it descends from a very old design idea: the creature that can only enter combat when the opponent has already committed to the sky. Lurking Green Dragon takes a body green almost never gets (a four-power flier) and pays for that intrusion into blue and red territory by making its offense conditional on the defending player controlling a flier of their own. On defense the restriction costs nothing: it blocks anything airborne all day, and the "can't attack" clause never touches blocking. The friction is entirely on the aggressive axis, which flips the usual read on an evasive threat. A 4/4 flier for four normally pressures the opponent to answer it or die; this one sits inert against a groundbound board and only comes alive once the opposition fields evasion, which is to say once they have committed to the exact plan the Dragon is built to punish. It is a threat that waits to be provoked, a green answer to flying that happens to wear a flier's stat line, and the timing of when it can swing is dictated not by its controller but by the opponent's own board decisions.