Hey, you know the library section "?" well that section is reserved for the monsters known as evil lords. Evil lords are the bosses that guard that catergorized gates(such as master mind, control and demolition this also includes the monster durran). These are special monsters for two reasons 1: to be the most powerful type of monster and 2: once you beat all of these monsters watabou will be your pal!
These monsters will not join you once you beat them but you can breed them! The only one iv found is dracolord. You breed draco lord by starting with a greatdrak(dragon and battle rex) then breed it with a servant(skeletor and skeletor)