Vulgar

The Vulgar is a monster introduced in Doom 3: Resurrection of Evil. It resembles an Imp although there are some bodily differences. The Vulgar have only two eyes that have an orange glow. They are slightly shorter and have a monkey-like frame instead of human. Due to this, they move on all four legs but will sometimes stand up on their hind legs when angered. Unlike the Imp, they sport a long tail, their bellies have small insect-like limbs attached to them and their lower jaw is designed like an insect's mouth parts. They also differ from the imp because they have plasmaballs instead of fireballs. Their plasmaball attack is comparable to the Hell Knight's version, though it is significantly weaker - even weaker than the Imp's fireball, though Vulgars take much less time to aim their plasma balls before throwing them. The other attacks consist of leaps and claw slashing. They have a mechanical-like growl that they emit in each attack and are capable of crawling on walls and other surfaces. Also, unlike other monsters, its spawning cloud is cyan rather than orange.

The Vulgar throws its plasmaballs in a lower arc than the Imp's fireballs. As a result, they travel in a straighter line and are easier to grab with the Grabber. Firing their own plasmaballs back at them with the Grabber is probably the best way to defeat Vulgars, as a single direct hit should kill a Vulgar instantly.

The Vulgar was originally planned to appear in Doom 3. It was stated to be the Arch-Vile, but was scrapped and its appearance was saved for the expansion pack.

Notably, as the Imp was the most prevalent demon in the original, the Vulgar is easily the most present demon with the most appearances throughout the expansion.

Appearance
The appearance of the Vulgar resembles species 8472 from Star Trek: Voyager or the Xenomorph species from the movie series Alien 1-4.

Trivia

 * There is another variant of the Imp in the game code, which walks in all fours in a quicker fashion. Although this version of the Imp was never present in the single player campaign and the expansion pack, it displayed almost identical behaviour as that of the Vulgar.
 * The Vulgar appears in every level of Resurrection of Evil, excluding the first level. However, it is one of the only standard enemies that does not appear in Doom 3: The Lost Mission.
 * The word vulgar means "indecent; obscene; lewd."
 * Unlike most other enemies, when the Vulgar teleports in, it appears in a cyan flash of light rather than an orange one. There is no explanation for this.
 * Because the Vulgars move more quickly than Imps, and therefore damage the player more quickly, they help force the player to rely more on the Grabber and Artifact.