- “Slay the Demon on SIGHT!”—Tartarus as John-117 infiltrates High Charity.
"Demon" is the Covenant name for all SPARTANs, but is most commonly used in reference to John-117 specifically. This is primarily due to the fact that the Covenant fear the SPARTANs, because of their ability to destroy hundreds or thousands of Covenant soldiers. The Covenant particularly fear John-117 because of his destruction of Installation 04 and killing the Prophet of Regret; because they treat Forerunner creations as sacred relics and the Forerunners as gods, it is possible that John-117 earned this moniker as a result of his destruction of the fourth halo ring.
Demon could also possibly mean a particularly powerful foe, and the Covenant might designate SPARTANs "Demons" because they rarely ever die, comparable to a demon's immortality, and are bringers of great destruction and defeat (just as John-117 destroyed Installation 04). The idea that Demons refer to powerful foes instead of only SPARTANs is, however, disproved in Halo 3: ODST, where enemy Unggoy refer to the player, who assumes the role of an ODST, as an "imp" which could technically be a small demon. Though some evidence toward Demon universally regarding a powerful foe is the fact that after the Arbiter seen in Halo Legends defeats a small army single-handed, a surviving Unggoy screams "He's a Demon!" before Fal 'Chavamee kills him, although he was also seen as a heretic.
In gameplay, when Covenant warriors encounter John-117 in combat and sight, they usually engage him with extreme caution. Unggoy and Kig-Yar have a tendency to retreat upon the Demon killing their Sangheili or Jiralhanae commander, or if they are the only soldier remaining. The San 'Shyuum and Jiralhanae also refer to John-117 as the Demon. The Prophet of Truth is the only member of the Covenant that has ever referred to John-117 by his alternate name of Master Chief. It is theorized that Truth says this so the player knows who "the Demon" is, as the term is not used in Halo: Combat Evolved. (However, in Halo: Combat Evolved, enemies will refer to you as a "devil"; upon spotting you, for example, Unggoy will sometimes say things like "Die, devil!" This may be a slightly inaccurate translation of the Covenant word for "demon," since the translation software used during Halo: Combat Evolved is not as advanced as that used during Halo 2, although it may be that they find John-117's large, physical appearance to be intimidating. Also in the Italian version of Halo: Combat Evolved Unggoy will call the player "Monster")
If any Covenant soldier actually kills a Demon, it may be assumed they are given a very high reward for their success against this potent and dangerous adversary. This can be noted in gameplay during Halo: Combat Evolved when John-117 dies, the nearby Unggoy laugh crazily or shout "I did it! I'm the one!" and similar things with the nearby Sangheili also laughing. In Halo 2 when John-117 dies, the nearby Sangheili say something along the lines of "The Demon is dead, I killed it! Me!"; "The Prophets shall reward me well for that!"; "The Demon is dead, by my hand!"; "I've earned my Journey!"; or, more rarely, "Ha! And I'm not even the Arbiter!". Unggoy can sometimes be overheard after John-117 dies exclaiming, "I get his helmet!"
When the player throws a grenade, Sangheili (and sometimes Unggoy) in Halo 2 will often yell, "Demon flare! Scatter!", regardless of the grenade type. Ironically, they will even shout this when playing as Thel 'Vadam, but that is due to universally applied combat dialogue.
- Main article: Halo 3
While fighting alongside allied Sangheili, they will call John-117 Demon, perhaps out of respect and deference, as a passive insult, or to signify his rank as a SPARTAN (this could be out of not knowing to call him "SPARTAN" or simply out of habit). Later in the game, the Sangheili begin clarifying and referring to John-117 as SPARTAN, or sometimes, human Champion; "The Human Champion is down!" The theory that "Demon" translates directly into "SPARTAN" is disproved in this game when Rtas 'Vadum and Thel 'Vadam both refer to John-117 as "SPARTAN" throughout the game. Thel 'Vadam, Minor Sangheili, and some Special Operations Sangheili will sometimes refer to John-117 as "Reclaimer", just like 343 Guilty Spark and the Ur-Didact. This is most likely as a result of the new Human-Sangheili alliance, which makes the derogatory term Demon inappropriate. The term was obviously taken from 343 Guilty Spark (who, as their "Oracle," holds a position of fervor among the Sangheili), who always refers to John-117 as Reclaimer. Despite this, Thel will nearly always refer to John-117 as "SPARTAN," as does Rtas 'Vadum.
- The way that the Covenant treat SPARTANs is similar to how the Space Pirates of the Metroid series treat their main enemy, Samus Aran, who they refer to as "The Hunter". Also both SPARTANs and Samus are super-humans that wear advanced powered armor, and both are capable of eliminating vast numbers of their enemies single-handedly with John said to have killed at least a thousand Covenant troops in one battle and Samus as having cleaned an entire star system of Space Pirates, both nearly single handedly.
- In Halo 3: ODST, an Unggoy can be overheard saying "Imp not as strong as Demon." upon the Rookie's death. Furthermore, the Jiralhanae may say "Yes, the Imp is dead. Now for the Demon."
- ↑ Halo: Ghosts of Onyx, page 243, "Voro strained to isolate the human word for demons from their objectionable speech... Spartans".
- ↑ Halo: Ghosts of Onyx, page 349, "They would take no chances with these human demons, these 'Spartans' ".
- ↑ Halo: Ghosts of Onyx, page 372 - "The Fleet Master Elite snarled at Kurt, and the translation filtered through his helmet's speaker: 'One last fight demon' ".
- ↑ Gravemind cutscene, "Kill the demon!".
- ↑ The Heretic cutscene, "But this demon, this Master Chief..."