Berserker Lord is the name of the theme that plays during both fights with the boss of the same name in Metroid Prime 3: Corruption. It is a remix of the Arachnus battle theme in Metroid Fusion. Both bosses are similar looking to one another as well. In Metroid Prime Trilogy, the theme has been added to the Soundtrack Gallery along with the Aurora Unit 313 theme. Both themes have replaced the Bryyo Thorn Jungle and Metroid Battle Themes that were originally available. The theme from Fusion can be heard here: [1] and the theme from Corruption here: [2].