I only can use the tier description pokémon to battle on tournaments? Or, for example, in OU tier, can I use any other pokémon which is not included on the others tiers of description in this forum? If i wanna use, for example, the pokémon Articuno, Dratini, Pidgey, Arbock... I can't? They don't are listed on any rank of tier in forum. I'm sorry for my english. I'm from Brazil.