The Circle of Doom is a roman gladiatorial style arena, where the evil warriors make people fight for their amusement.  After Fisto is captured, Evil-Lyn decides to make him fight for his life in the circle, fighting Clawful, Jitsu and Whiplash in succession.  When it looks like he may be destroyed by Whiplash, He-Man and Stridor enter the circle, stoppping Whiplash, and demolishing the circle from within!