Manor Gargoyle

Defender keyword and indestructibility are stapled together by a clever conditional: the wall is unkillable precisely because it stays home, and the moment you spend the mana to pry it loose for an attack, the protection drops with the keyword it was tied to. That linkage is the whole engine. As a 4/4 it blocks anything on the ground and shrugs off any burn spell, sweeper, or combat trick that relies on destruction while it stays the static body, then converts to a 4/4 flier for a single mana when you want to push damage or punch through stalled boards. The window matters: you activate, the keyword and the indestructible clause both fall away for the turn, and you have a fragile flier instead of an immovable wall. That repeatable flip means a player has to choose, every turn, between an answer they can barely remove and a clock they can. It rewards reading the board rather than committing to one mode. The design predates the modern glut of "indestructible while X" texts, and it remains one of the tidiest expressions of the idea: a single line of conditional indestructibility doing the work of both a creature-removal hedge and a mana sink, with the activated ability serving as the release valve that keeps the package from being purely defensive. A wall you can weaponize, on your own schedule.