Operation Siren (cn: 大型作战, jp: セイレーン作戦, kr: 대형작전, tw: 大型作戰) is a mid-to-endgame game mode introduced to the game on December 22th, 2020. The primary benefits of playing Operation Siren are the randomized maps that can be grinded without costing oil, granting some of the best gear in the game and offering the opportunity to do powerful Raid Bosses for META ships. Commanders need to be at least commander level 60 to start, with the story ending at enemy level 98, regular opponents at enemy level 114, and powerful bosses at level 130.