The Imp in Doom 3 is humanoid in shape, has grey skin with bony scales on its arms and 10 small eyes, Compared to its original version, and like many of the game's other demons, they have a more "alien-like" appearance. Unlike the "serpentine hisses" produced by their classic counterparts, this new version emits a high-pitched screech (although when starding guard somewhere nearby, the player could still hear a hiss and know an Imp is close). These monsters are tall and aggressive, and stand at approximately the same height as a normal human.
Imps are very, very common in the game, often being teleported into an area after a player enters it, or has performed some action. They are the most frequently encountered demon in the game, appearing 15 to 30 times more often than other demons. Moreover, they like to hide in front of doors leading to secluded areas or hallways, from where an Imp can leap directly onto the player once he opens the door.
In Hell, Imps have a different appearance than those encountered on Mars. Their skin is flesh-colored, making them appear to have been flayed. This fact leads some to think they are naturally skinless and their bodies adapted when exposed to the Martian environment.
The Imp makes its introduction in a cutscene where the marine walks past a door when he hears a strange screech and turns back to find the source of the sound; the Imp suddenly comes out from a narrow space between a wall and a huge steel gas pipe, crawling through the ceiling, jumps across to hang against a wall, then hops feet-first to the ground to face the player.
The Imp generally walks slowly towards the player, but it can climb walls as well (note that all Imp wall-crawling are scripted actions for when an Imp first enters an area. Once the scripted entry sequence has ended and they are on the ground, Imps are limited by their A.I. to normal walking). Most of the time, they will ambush the player, hiding behind doors or climbing on the ceiling. They can either throw explosive fireballs from their hands that travel in an arc, attack with their claws, or pounce forward more than 25 feet in a scratching attack. Occasionally, they will pounce sideways when hit to dodge additional fire.
The Doom 3 Imp can, in some ways, be seen as tougher than its classic counterpart, considering its ability to leap at the player in a surprise attack, its increased agility, and its fireballs, both by the smoke, which can easily obscure the player's vision, as well as their trajectory, since they are hurled more naturally in an arc (like a human throwing a baseball) rather than straight as in the original Doom. Fortunately, some of Doom 3's weapons are more powerful, most notably the shotgun, which has a similar amount of firepower to that of the classic Doom II double-barreled shotgun, and the chain gun. There are also other demons weaker than the Imp but, generally, it seems as weak as the classic Imp, taking a single shotgun blast at point-blank range to kill, though they sometimes survive such an encounter.
Overall, the Imp is an average mid-level demon, tougher than Z-Sec soldiers or "pest" demons such as Trites or Lost Souls, but still relatively easy to bring down. They are about on par with Maggots or Wraiths in terms of combat threat.
The shotgun is usually the best weapon to use against individual Imps, as a well-placed point-blank shot can kill it instantly, but players should be wary of their tendency to suddenly drop to all fours and pounce on the player. If this happens, grab your Shotgun and wait for them to pounce. You should either back up a bit so you are out of the Imp's pounce range, but still within close proximity to it, and shoot right when it has landed, or stay in range and, when it gets close enough, fire (the latter technique should NOT be attempted by new players, as they usually don't have the reflexes to do it, unless they are familiar to this tactic from another game. The Imp may not do much damage, but it can still be deadly, even if there is only one). This usually gives a one-hit kill. Players should aim for the upper part of their bodies and move in as close as possible as the Imp's thin stature makes it difficult to hit it with the full spray of pellets even at the slightest distance. One more thing to take note is that during the 2-3 seconds of time when the Imp is first summoned and is squatting down, don't hesitate to empty your shotgun at them. They will be inactive during this time, so it is safe to get closer to the Imp and kill it.
15 to 20 rounds of Machine Gun fire can also bring down an Imp, and has the advantage of being able to mow it down from long range outside the range of its pouncing and melee attacks. Against multiple Imps, more powerful weapons such as the chain gun and plasma gun are advised. Imps have been observed (sometimes) to be somewhat bounded in certain areas, meaning that Imps will cease chasing after the player has escape an Imp's guarded area. In this state, the Imp may only shoot its fireball and return if the player is still within its sight.
Evading its fireballs is fairly easy once players get used to their traveling arc. Moving forward and ducking whenever the Imp tosses its projectile is the easiest way to avoid being hit. In more open areas, strafing sideways also works if there's enough space to do so. Their fireballs have minimal splash damage, causing only a couple points of damage, so take that into consideration when dodging. If you have the Grabber (in Resurrection of Evil), you can catch the fireball and shoot it back at them; a direct hit should kill it. It will be one of the first uses you will have for the weapon; the soldier who gives you the Grabber is shown doing just this and tells the player about it before turning over the weapon. Imp's fireballs are known to have a certain degree of "friendly fire". Combined with an Imp's territorial nature, it is possible to neutralize two Imps with 14 pistol rounds.
UAC Research Notes
These notes can be downloaded to the player's PDA during the course of the game:
Specimen 197 - Imp
This humanoid's long and muscular limbs make it extremely agile as a biped or quadruped. Its long and sharp claws allow for climbing steep surfaces. A configuration of 10 eyes provides this creature with a wide field of vision and the ability to see with clarity in low-light environments.
Specimen 27 - Imp (partial)
-Left forearm amputated for biological study.
Researchers are currently studying how this creature is able to manifest and throw an explosive plasma projectile from its hands.
- There are actually 2 different types of Imps in the game code; the regular imp that walks normally, and a quicker version of the Imp that always walks on all fours. This second version of the Imp is not actually used in the single player campaign, presumably being replaced by the Vulgar in the expansion pack, as it displays nearly identical behavior. However, this version of the Imp often appears in fan-made levels, as well as in the Lost Mission campaign included with the Doom 3: BFG Edition.
- The Doom 3 Imp shares some similarities with the Reaper Splitter from TimeSplitters 2, both being humanoid creatures with grey skin. They also possess similar attacks, with the Reaper Splitter hurling blue energy bolts comparable to the Imp's fireballs.
- The Doom 3 Imps behave similar to the Lickers from the Resident Evil series.
- The Imps found in the 2005 movie closely resemble the Doom 3 Imp.