|This article is written from the Real Life point of view|
In all its variations, the most distinct feature of the theme is its iconic rhythm: a repeating pattern of four beats followed by two short notes, with the first four beats played on a single pitch. This rhythmic pattern is somewhat similar to the ones heard in Vs. Ridley and Slench, though with a greater number of long notes compared to short notes. The melody of the song tends to be slower and set in a high register.
In Fusion, VS. Mulcalah serves as the fast-paced battle theme for Arachnus. Due to the Game Boy Advance hardware, VS. Mulcalah has very electronic MIDI instrumentation. While it is a little suspenseful, the theme comes across as less serious than most Metroid boss themes. After the song has looped twice, it proceeds to a new section of the song.
VS. Mulcalah can be heard here: 
As its name implies, Berserker Lord acts as the boss theme for both Berserker Lords encountered aboard the G.F.S. Olympus and in Eastern SkyTown, Elysia. Although it still uses electronic instrumentation for its melody, the theme has been filled out with more orchestral sounds. Overall, it sounds darker and more sinister, especially when it builds up to a dramatic series of minor chords played on an organ.
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.
Berserker Lord can be heard here: 
In Metroid: Samus Returns, the theme was remixed by Daisuke Matsuoka, as the theme associated with the Diggernaut. It first made its debut in the Official Game Trailer, and was frequently used in other advertisements such as Overview Trailer and Infiltrating SR388.
A slightly different, shorter variant of this remix plays during the Diggernaut chase sequence in Area 4; this version is appropriately named Boss Manic Miner Chase. The full version, titled Boss Battle 6 or Boss Manic Miner Bot, plays during the Diggernaut battle in Area 6.
The Boss Manic Miner themes are by far the most frantic and aggressive version of the theme, with low brass instruments relentlessly pounding out the iconic rhythm. The instrumentation is almost entirely orchestral, though there are machine sounds and electronic effects added to emphasize the Diggernaut's robotic nature. While most of this remix focuses on the rhythm, an instrument resembling an electronic organ performs a variation of the original theme's melody at one point.
- Arachnus and the Berserker Lord, who share this boss theme, are also the first bosses fought in their respective games.
- Ironically, although it also appears in the game, the Arachnus received an entirely new theme in Samus Returns instead of a remix of VS. Mulcalah.