You had to catch the legendary beasts and then get the Rainbow Wing.
... I never could catch Entei>>
@mata: If there are odd numbers we can always make a round robin to start off, and the lowest scoring would leave(for example, we start with 10 people, two groups. After the round robin, we're left with four people from each group-> eight total).
Prizes that would be cool: any event pkmn, feebas/milotic, Macho Brace, a Power item, rare berry, perfect EV trained pkmn(I dunno which one, maybe a starter...)