Stadium/Flame Cup/6

Reward:  2 and 31500

Strategy:  Gummy is ideal for Dark Fire, because it is resistant against its dark attacks, its Rotting spell deals double damage and neither Butterfly nor Robot have efficient attacks against Gummy. For Butterfly, Cool Fire is most efficient, with its ice attack and resistance against both of Butterfly's elemental attacks. For Robot, both Gummy and Petroleum (and to some extent Pirate) can provide powerful attacks and decent resistances. If you have a Pure Dragon, its Pure Energy attack will be devastating for Robot.

Of course, strong Pure Elemental Dragons will eat these 3 up really good (Pure Terra/Nature for Dark Fire, Pure Terra/Ice for Butterfly and the plain Pure for Robot).