This theme is heard when Samus Aran is about to confront a boss character in the vicinity, often foreshadowing the presence of a boss character: specifically, Kraid, Phantoon, and the Big Metroid. It also plays in the immediate aftermath of the Crocomire boss battle, as the creature's skeleton swims through the lava.
An alternate version of the theme briefly plays as the first Torizo breaks out of its Chozo Statue. This version is slower in tempo, lower in key, and removes the melodic bass line, leaving just the harmonic strings; the result is less intense, but even more eerie.
- In the game proper, only about five seconds of the Torizo variant can be heard before Big Boss Confrontation BGM (Ridley, Draygon) starts playing. However, the full song can be faintly heard by pausing the game at the right moment.