Marvel_Mystic
Both are sorcerers that specialize in black magic. Which one is Strange's more powerful foe?
http://marvel.wikia.com/Kaluu_%28Earth-616%29
http://marvel.wikia.com/Karl_Mordo_%28Earth-616%29
http://marvel.wikia.com/Kaluu_%28Earth-616%29
http://marvel.wikia.com/Karl_Mordo_%28Earth-616%29