The Strong Shell are recurring bosses in the Darius series, usually appearing as final bosses. Shaped after the sea turtle, the Strong Shell series are based on one of the original Thiima battleships. They specialize in defense and firepower, while lacking speed and mobility.
Their outer shell actually serves to conceal a variety of weapons, which includes lasers, rocket launchers, missiles, machine guns and so on, up to the burst guns in the later revisions. Their head is their only weak spot, but they are able to conceal it inside the outer shell while still firing. Their huge arsenal more than makes it up for their lack of movement.