Wraith/Doom 3

The Wraith is a monster in Doom 3 and the expansion pack. Wraiths are limited to melee attacks with their falx-like arms, and run forward to attack the player. They possess the ability to teleport, disappearing for a couple seconds before reappearing a couple dozen 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 target profile. Furthermore, Wraiths have only two eyes and a set of mandible-like jaws. The Wraith first appears in the EnPro Facility.

Tactics
Like Imps and Maggots, Wraiths are mid-level humanoid-type demons who are individually relatively easy to dispatch, but who can attack in groups of up to several in the same area.

Wraiths cannot be killed while teleported, however it takes them about a second to disappear or reappear, during which they cannot attack and are vulnerable to being damaged or killed.

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 machinegun from medium range.

They are extremely vulnerable to being chainsawed during their second-long appearing or disappearing animation.

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.