Filled with hidden surprises, developer id Software's new Doom has a sinister message tucked away in its soundtrack. Reddit user TomButcher recently found that at least one tune in the Doom soundtrack, Cyberdemon, shows hidden pentagrams and the infamous "number of the beast" – 666 – when the music's frequencies are displayed through a spectogram.

Doom's composer Mick Gordon, who recently teased the presence of hidden demonic imagery in the game's soundtrack in a YouTube video (around the 3:29 mark), also confirmed the existence of the creepy Easter egg on Twitter.

Considering the fact that the first-person shooter is all about battling vicious demons and other diabolical entities, the cool little Easter egg is yet another example of the id Software team's impressive attention to detail. Other hidden Easter eggs in the game include a reference to Terminator 2 and slices of the original 1993 game and its sequel hidden in each level.

The latest addition to the hellish Doom franchise has been well-received by both critics and fans, and is currently holding on to the No 2 spot in the UK sales charts.

IBTimes UK's review of Doom's 2016 reboot also lauded the game for its fast and fluid movement, interesting enemies, and sprawling environments.

"Intelligent, fresh and endlessly enjoyable, Doom is more than a tribute to its beloved progenitor," it reads. "Taken in its own right, this is the most finely crafted, technically impressive pure shooter in over a decade, proving that id Software, even after 26 years, is an adept, sophisticated game-maker. It may not create the same tectonic shift in video game culture as its ancestor, but personally, I prefer this Doom to the original. By refining, meticulously, several age-old and taken-for-granted game mechanics, Doom proves that excitement, spectacle and even narrative cohesion can exist in games seemingly composed of the basest elements."

Released on 13 May, Doom is out now for PlayStation 4, Xbox One and PC.