Format-Gen 6 pokebank
LEAGUE LAYOUT
The Skull League is not like other Leagues. Rather than defeating gym leaders, you are defeating the self-named rulers of each sector of the Urobad Region (aka, mercenaries). Defeat all the mercenaries with your preset team in a sector to gain access to the sector's Castle(s). With each Mercenary you defeat, you gain a new Pokemon, but you can't get new ones in the Castles. Once you defeat the sector's castle(s), that sector is safe and you can work to liberate the next sector. Be careful, though; take too long to clear a sector, and the mercenaries will come back!!