Imp/Doom 3

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 standing 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 common, appearing more frequently than many other demons. This could suggest that Imps serve as the primary foot soldiers of Hell. They often teleport into an area after a player enters it, or has performed some action. Moreover, they like to hide in front of doors leading to secluded areas or hallways, from where an Imp can leap 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.

Combat characteristics
From long range, Imps throw explosive fireballs from their hands that travel in an arc and attack with their claws at close range. On occasions, they can also pounce forward in a scratching attack, or lie in ambush by hiding behind doors or climbing on the ceiling to pounce at the player. They will sometimes leap sideways when hit to dodge additional fire. Imps can also climb up on walls and ceilings, although this is generally limited to scripted events.

Tactical analysis
The Doom 3 Imp is tougher than its classic counterpart. It is a lot more agile and has gained the ability to pounce at the player from great distances. Its fireballs can also obscure the player's vision from the smoke, and the fireball's trajectory allows it to be hurled more naturally in an arc (like a baseball being thrown), rather than straight as in the original version.

The Shotgun is usually the best weapon to use against an individual Imp, 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. 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.

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".

Overall, the Imp serves as a lower middle-tier demon; they are on par with Maggots and Wraiths in terms of combat threat, making them more threatening than a Z-Sec, but trivial compared to a Demon.

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.

Trivia

 * 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 hurling energy bolts from a distance. They also share similarities to another humanoid creature known as Lickers from the Resident Evil series, both possessing high agility to pounce on their prey while crawling up on walls and ceilings.
 * In the Alpha version of Doom 3, the Imp emitted an animalistic snarl accompanied by the Hell Knight death audio from the classic games.
 * The Imps found in the 2005 movie closely resemble the Doom 3 Imp.