Wraith/Doom 3

The Wraith is a monster in Doom 3 and its expansion packs. Wraiths are limited to melee attacks with their -like arms, and run forward to attack the player. They possess what appears to be a "teleportation" ability, disappearing for a few seconds before reappearing several feet ahead of their previous position. It can be easily mistaken for an Imp while it's being summoned. Unlike an Imp, Wraiths are hunched over and present a lower, wider target profile. Furthermore, Wraiths have only two eyes and a set of mandible-like jaws, and look more like a bat than a human.

The Wraith first appears in the EnPro facility, though its debut cutscene doesn't appear until the end of the level. In the gruesome cutscene, the hero finds another Marine, who is mortally wounded and gives the hero a transmission card. The monster is shown to stealthily climb down a wall, right behind both Marines, then hides in cover for a single second before leaping onto and killing the wounded marine before facing the player with its jaws splitting open horizontally, letting out a frightening scream.

Combat characteristics
Like Imps and Maggots, Wraiths are mid-level humanoid-type demons that are relatively easy to dispatch individually, but who can attack in groups of up to several in the same area. When paired with other Hellspawn, the danger they present increases, as they are fast enough to block the player in, and attack while they are distracted with other threats.

When they "teleport," a pentagram appears on the ground where they are standing and fiery orange streaks shoot up as they disappear. Once the Wraith fully disappears, so does the pentagram on the ground. At this point, the Wraith is invisible, but is still bounded by physical objects, such as doors, shelves, crates, etc. as it moves about, and its footsteps can even be heard. A few seconds after disappearing, another pentagram appears on the ground where the Wraith is currently standing and the fiery orange streaks then move down the Wraith's body as it reappears in the center of the pentagram. Once the Wraith fully reappears, the pentagram again disappears, and the Wraith is then free to move and attack the player.

Wraiths prefer ambush tactics, even after being seen. They try to teleport themselves to places where the player is not looking to ambush them. Though their attacks do little damage, they should not be underestimated, as they move and attack quite fast. They can easily pin and seriously damage a distracted player.

Tactical analysis
Wraiths cannot be killed while teleported, however it takes them about a second to disappear or reappear, during which they cannot attack or move. This makes them extremely vulnerable to being damaged or killed. They can easily appear to attack the player's flanks, and their rapid and often erratic movement makes them difficult targets.

It is a good idea to throw a grenade their way. Another good tactic is to wait for them to get close and eliminate them with the chainsaw or the shotgun. In addition, they can be easily eliminated with the machine gun or plasma gun at medium range.

Trivia

 * In the Making of Doom 3 book, Id wanted the Wraith to form out of a cloud of insects, to hide in bodies and such, but this concept was scrapped since the player wouldn't even be able to tell what the cloud was in the dark environment.
 * The Wraith's teleport ability may not be exactly teleportation. For one thing, it is not instantaneous. Also, while teleported, they still cannot travel through solid objects such as crates, shelves, or walls, and when they teleport through doors, the doors will open. Furthermore, their footsteps can still be heard after they disappear. This suggests that Wraiths don't actually teleport, but rather "phase" into a state of existence where they cannot be seen or attacked. If that is the case, then they would be similar to that of the Spectre. However, these might be merely distracting illusions or gameplay element.
 * Interestingly, the Wraith is the only enemy in the game that the player starts fighting before it makes its debut cutscene, perhaps because it's easily confused with the Maggot.
 * In the 2016 reboot of Doom, the term "Wraith" is used to describe what appear to be completely different species that are not native to Hell, but have been corrupted by the demons. While looking different there are some potential links between them. In Doom (2016) it is established that Wraiths are highly suceptible to Hell energy and it can change their forms. What is seen in Doom (2016) is likely not their own original forms before the demonic evolution. It may only be one form of 'evolution' due to exposure by Demonic energy. It is also said that forces of Hell captured Wraiths, transformed them to use in their forces. Because there is a potential for any number of evolutions and mutations its still possible for the Wraths of Doom 3 and Doom (2016) to be related somehow. Both Doom 3 and Doom 2016 wraiths are dark colored, and have insect like aspects. Both appear to have similar jaw (lower jaw splits into what look like mandibles with two claws/teeth turned side ways towards each other from each mandable) and facial structures (though Doom 2016 versions have far more demonic aspects such as horns growing out the top of their heads). While DOom 3 has fewer appendages, its two upper arms still appear to have 'bat-like' membrane stretched between their arm and body (Doom 2016 have more of this membrane between each appendage). The forarm ends in what looks kinda like a praying mantis or scythe blade, the wraiths most prominent appendages also appear to end in what looks like a scythe like blade.