To unlock Prototype Raiden for play, beat Arcade mode with Raiden. Then, at the character selection screen, highlight Apharmd B and press X. Highlight Apharmd S and press X. Highlight Dordray and press X(2). Highlight Specineff and press X(2). Highlight Fei-Yen and press X(2). Finally, highlight Cypher and press X(3). Prototype Raiden has increased damage, but cannot use turbo weapons, air dash, or double jump.