The Order of Assassins (siglum: OOA) is one of the most famous and feared organizations of Elysion (something like mafia). The Assassins are divided in classes by the level of their most powerful technique - if it's S-rank the Assassin is a 1st class, if it's A-rank the Assassin is a 2nd class etc. Main Location: Empire-Kingdom of Mer - Mer Island - Mer Plains - Mer City - OOA Headquarters. Active Members: All the existing Assassins (1500+).