Double Dealer is the boss of zones L and N in Darius Gaiden. It is shaped after a flounder.
On zone L, Double Dealer will begin his attack by releasing floating mines which shoot at the player if not destroyed in time. He will also attack by shooting lightning bolts. After a while he will begin shooting large bullets across the screen and releasing homing missiles. After taking enough damage, he will turn around to show his other side, then begin the second phase of the fight. He will release fish drones who go after the player and shoot green bullets, as well as triple balls which explode into three purple lasers. After this he will shoot large bullets in arcs which are tough to dodge. His last attack is to shoot fast purple lasers aimed at the player.
On zone N, he will first use the large bullet spread then release the floating mines and shoot lightning. After this he will shoot purple homing lasers. On the second phase he will use the large bullet spread while sending the fish drones at the same time, then shoot the large bullets in a clockwise motion while releasing the triple balls, after which he will shoot the large bullets in arcs and the fast purple lasers.