Omega Weapon? In the Castle: From the entrance, take your figthing party to the fountain with a green switch circle. Now, prepare your party and then switch to the other party. Take the non-figthing party up the stairs and then turn left. Go trough the door and down the stairs in this room. This is the room rigth before the room with all the paintings. Walk towards the screen and press X. Now, a countdown will begin and you have to switch back to the figthing party and go to the room with the purple mist thing. Omega is waiting rigth there. If the countdown reach 0 then Omega will dissapear.