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 give players a sizeable amount of lux upon defeat, as well as EXP or evolution medals. Every time you defeat a raid boss you summoned, it goes up a level. When you next encounter the raid boss, it'll be stronger, and will also give more lux as well as a chance at better medals compared to before. Each raid boss has its own individual level.
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 all the same rules as normal raid bosses except that they have a twenty minute timer instead. They are noticeably different visually, displaying an alternate colour scheme compared to their lesser forms.
Much like their lesser counterparts, Omega raid bosses also have their own individual levels.