Loyal Gyrfalcon

The wall that decides when it stops being a wall. Defender on a 3/3 flyer is the cost; casting a white spell is the toggle that turns it off, just for the turn, converting a blocker into a three-power evasive attacker on the same turn you were going to develop your board anyway. The design tension is in the conditional: the body is permanently shackled until your own play pattern unshackles it, which means the creature rewards a deck already pouring white mana into spells and punishes one that taps out for off-color threats. It is a defensive piece that quietly wants to be aggressive, and the line between the two modes is drawn by your spell color rather than by combat math or a mana investment in the creature itself. Note the timing window: because the trigger fires on cast, the defender drops before the spell resolves, so the attack is live in the same main phase you commit the spell and lasts through your combat step regardless of whether the spell is countered. That is the wrinkle that separates it from a creature that simply gains a keyword when something resolves. As a piece of white-weenie scaffolding it asks for a low curve of one- and two-drops to flip it reliably, which is both its appeal and its ceiling: the falcon is only as menacing as your white spell count is dense.