Raid Boss
Raid Bosses are unusually powerful Heartless which are encountered after killing approximately 70-75 Heartless. Raid bosses only last 10 minutes before disappearing, and cost zero AP to fight. The Raid Boss spawned depends on which mission you last completed.
Raid Bosses all have at least one weak point which can be targeted; defeating one of these weak points delays the enemy's turn by one round. If you fail to defeat the raid boss you have spawned, party members can pay 10 AP to assist you for a chance at the same rewards. Even if a party member defeats your raid boss, both of you get the same amount of Lux and basic medals.
Omega Raid Bosses
Omega raid bosses are a rarer version of each raid boss. They are more powerful and grant greater rewards, but follow the same rules as normal raid bosses.