The Shadow Boss is the leader of the Shadow Warriors in Battletoads and Double Dragon, having allied himself with the Dark Queen. He appears as the boss of Stage 6 and mainly attacks by leaping at the 'Toads and Dragons. If he can get close enough, he'll grab the player and strangle them while bashing their heads. His most dangerous attack is when he turns into a spiked ball and bounces back and forth across the screen. The only way to avoid the attack is to hang onto the lamps above (assuming the player didn't already destroy them for power-ups).
The Shadow Boss was created solely for the game and has not appeared in any Double Dragon games. However, he bears a resemblance to a masked boss character named Burnov from Double Dragon II, though Burnov was fat whereas the Shadow Boss is lean and muscular.