Vulgar

The Vulgar is a monster only exclusive to Doom 3: Resurrection of Evil.

It is a medium-sized quadruped demon resembling Imps in many aspects. It has a human skull-like face with glowing orange eyes, a monkey-like body frame with a long tail, an abdomen that have small insect-like limbs, and insect-like mandibles on their lower jaw. They make a loud respiratory sound (similar to breathing through an oxygen tank) when they are present, but emit a high-pitched mechanical growl when they spot the player.

The Vulgar was originally planned to appear in Doom 3 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.

Combat characteristics
The Vulgar in many ways, behaves identically to the Imp; throwing fireballs at a range, and occasionally leaping at the player or clawing them up close.

The most obvious difference, however, is that the Vulgar throws a bluish green fireballs, similar to that from a Hell Knight, although it's much smaller and significantly weaker.

The Vulgar's overall attacks do a lot less damage compared to those from the Imp. To make up for this, Vulgars possess better speed. They can move and execute their attacks a lot quicker than Imps, while throwing its plasma ball in a lower arc than the Imp.

Vulgars also appear in larger numbers than Imps, as they frequently come in pairs. While Imps are limited to appearing in between two or three and rarely more in one area, Vulgars can appear in group of four to five, although they are only limited to two in one area; if one Vulgar is killed, another Vulgar will start spawning.

Tactical analysis
While the Vulgar possesses a lot less powerful attacks than the Imp, they generally make up by moving a lot quicker to close in on the player, and even executing their attacks at a much faster pace. Combined with the occasion that they can come in more numbers than Imps, Vulgars can be a bit more dangerous if left unattended for a while.

A Shotgun blast at point blank range is generally sufficient to quickly take down a single Vulgar. However, as they are more likely to quickly execute their attacks, players are risking themselves taking damage up close from their clawing attacks. On the other hand, the player is introduced to the Super Shotgun, which can instantly take down a Vulgar without the risk of standing very close to them. As Vulgars have the habit of throwing their fireballs at a much lower arc than those from Imps, the Grabber is also another effective weapon, as their fireballs travel in a straighter line, making them easy to catch. Firing their own plasma balls back at them with the Grabber is another way to effectively defeat them.

Because the Vulgar are much quicker than Imps, relying on the Artifact can generally be a more effective way to slow them down. This should only be reserved when players are forced to fight a multitude of them, as the limited amount of human corpses available to charge the Artifact would make a single or even a pair of monsters become a wasteful usage on resources.

Trivia

 * There is another variant of the Imp in the game code, which walks in all fours in a quicker fashion, while hurling the fireballs in a much lower arc in quicker succession. Although this version of the Imp was never present in the single player campaign and the expansion pack, it displayed almost identical behavior 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 appearance of the Vulgar resembles Species 8472 from Star Trek: Voyager or the Xenomorph species from the Alien series.
 * The word vulgar means "indecent; obscene; lewd."
 * Interestingly, the Vulgar is the only enemy in the game, even in the expansion pack, whose spawning cloud is cyan in color, rather than orange.