Mephistopheles Theme is an unlockable easter egg song found in the Call of Duty: Infinite Warfare Zombies mode. It is heard during the fight with Mephistopheles and can be selected as lobby music upon completing a small easter egg.
Unlocking the Song
To unlock the song as lobby music, the player must first complete all five main easter eggs and unlock Director's Cut. Once the player starts a game of The Beast from Beyond within Director's Cut, the player must reach the real world Afterlife Arcade before the beginning of Round 2. The player must interact with the Octonian Hunter game, causing a Talisman Mask to appear and act like the UFO in the game. Shooting it will grant the player Mephistopheles Theme, as well as the theme for Extinction and the Afterlife Arcade as well for the player to use a lobby music.