Osiris Suite, Act 3 is the thirty-fifth track included in the Halo 5: Guardians Original Soundtrack.
The first section is used during the closing cinematic of Before the Storm. The second portion is used during the second half of the Mantis run in Swords of Sanghelios (level) and during the opening cinematic of Battle of Sunaion (level). It also plays as battle music for the first part of the Battle of Sunaion as well. The third section is used as ambient music during the first part of Swords of Sanghelios and it also plays in Battle of Sunaion when fighting in the undercity. The final section is used during the closing cinematic of Battle of Sunaion.