Logos is a boss in Final Fantasy X-2. He is fought with his partner Ormi multiple times, in a way not dissimilar to Biggs and Wedge and Ultros in previous games. He is fought one less time than Ormi, who has the title of most recurring boss in the game.
This fight is easy, as it is a tutorial type fight. The player can simply use the Songstress abilities to limit Logos's actions and pound away at him with physical attacks. Ormi deals more damage than Logos but Logos can use Potions to heal himself or Ormi.
Logos gets a bit harder here. The party should bring several Eye Drops and Echo Screens to counter Silence and Blind. If the party has Sleepy Shuffle it may be useful as Logos only has a 30% chance to resist it, and makes the fight that much easier.