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Bosses refer to any major enemies that appear in their own unique arena at the end of a mission. There are a total of twelve bosses in Phantasy Star Universe, eight introduced by the base game and four added by Ambition of the Illuminus. This article lists all twelves bosses as well as the permanent missions in which they appear. (Event and story missions are excluded as the former are only temporarily available and the latter do not offer boss drops.) Individual item drops are not listed, however, as they are handled on a mission-by-mission basis instead of a level tier system like normal enemies.