Lost Soul/Doom 3

The Lost Soul in Doom 3 is a head-sized flying demon consisting of a human face mounted on a flying rocket engine contraption. Its jaws are torn apart to allow it to open its mouth wider than a normal human could and its teeth have mutated to long, pointy, needle-like teeth.

They hover through the air at average speed, and attack by abruptly rocketing in a straight line towards the player at high speed and ramming into them, similar to the classic Lost Souls. Unlike the classic Lost Souls, Doom 3 Lost Souls can cover a larger area and can change course if necessary and the classic Lost Souls are giant, flaming, flying skulls with sharp teeth. The Doom 3 Lost Souls are flaming flying human heads. The Lost Soul is usually found in packs with other Lost Souls (which was often the case in the classic Doom games as well). The Lost Souls can be problematic opponents if the player does not manage to kill them quickly. They first appear in the Mars City Underground in a more skull-like form (similar to its classic version), and they appear to be responsible for possessing humans and turning them into Zombies, the first zombie encountered being Jonathon Ishii, they also appear stalking the player throughout the Underground, but they don't attack.

Their first appearance as enemies is in the EnPro facility.

The first proper appearance of an Lost Soul as an enemy occurs in a grotesque cutscene with Theresa Chasar, one of the few female UAC employees. When the marine approaches, she whispers "help me", then her facial skin starts to shrivel inwards while acquiring a horrible pale color, and a Lost Soul bursts out of her head, ripping out her spinal cord in the process. It could be possible that a Lost Soul needs to manifest itself within a body, this is supported by the cutscene and the rest of the lost Souls could have come from the bodies with the damaged faces as well as the ones without heads, however this might not be true as it might have been a coincidence, teleporting at the right time, but does not explain Theresa's behavior, heavily supporting the first theory.

They are also considered some of the most annoying enemies, as they can often knock the player off a ledge to their death.

Compared to the classic version, Doom 3's version of the Lost Soul is very weak. It can be taken down by a single punch if necessary and it 2~4 pistol bullets to kill. However, their smaller size makes them more annoying than the classic version, especially if they attack in swarms, and one missed shot from an individual Lost Soul would give it enough time to retaliate against the player. The Machinegun or the Plasma Gun are the most efficient weapons for taking down a horde of them, thanks to their high accuracy and rapid rate of fire.

One risky way to kill them is to use Shotgun, fire while it charges at you, you should get an insta-kill if it's about 2 feet away from you, make sure no one is flanking you before try this.

The Resurrection of Evil and The Lost Mission expansion packs replaced the Lost Souls with a new monster called the Forgotten One, which bears a closer resemblance to the classic Lost Soul, just use Grabber on them.