The Master of the Hellish Yard stands before a box with a golden key to unlock it. Observing her surroundings, she realizes that she is in a hell. She plans to overthrow this hell, claiming it shouldn’t have existed and the time has come to reduce it to nothing. She continues to state how, as the sins had been branched off into seven and made the space into a hell, she has now been given the mission to end it. She notes how putting in the golden key will change everything from the forest, using a certain "boy" to create "Punishment". Declaring she would finally find death, she claims that the hell called Evillious shouldn’t have existed. With the assassin turned dictator letting loose her punishment, someone curses out everyone.
The Muzzle of Nemesis shows the backstory of the Master of the Hellish Yard, showing the events that turned her from an assassin to a dictator as well as the events that led to her becoming Master of the Hellish Yard.
The song's events parallel the Trinity test conducted in New Mexico, USA, the first test of an atomic bomb by the United States army.
The Master of the Hellish Yard's statements that she had become "Death, the destroyer of all" likely references J. Robert Oppenheimer's famous quote from the Bhagavad Gita: "Now I am become Death, the destroyer of worlds."
Similarly, the song's unidentified quote towards the end likely references the same quote by Kenneth Bainbridge: "Now we are all sons of bitches;" it was stated to Oppenheimer immediately after the Trinity test was successful.
Prior to the song's announcement, mothy posted a poem entitled "Nemesis" on twitter, seemingly alluding to the events portrayed in the song; at the end of the poem, mothy stated it was a late night work and didn't have any meaning.