The Rook is the key defensive piece in Chess, with its row and file control, it defends the back rank from advancing pawns. The Rook's unique ability to castle, creating a stronghold for the king, requires swift movement that is achieved through the airlift via the heavy-payload castle-drone. *Note that the rook can only utilize its drone's airlift-castle-maneuver if it is its home-turret position. (The resemblance to the elephant pays homage to piece in medieval Indian chess, that was a precursor to the bishop.)