The Forgotten Ones' form is an echo of the original Lost Soul's shape in the first two Doom games, replacing the reinterpretation in Doom 3. They are exclusive to the Resurrection of Evil expansion pack.
It is a flying skull with two demon horns, when it floats its flame stream behind it.
Its only attack consists of flying towards its enemy and biting. Unlike the Lost Souls in standard Doom 3, Forgotten Ones do not moan and scream upon detecting the player.
Due to the lack of melee weaponry, these enemies are much more difficult to eliminate than the original. As in Doom 3, the use of the chainsaw or weak weaponry can result in immediate death, however this incarnation has the potential to withstand a standard shotgun blast from mid-range. On the other hand, the player has a new advantage over them; they can be caught by the Ionized Plasma Levitator (aka the Grabber). Once grabbed, they can still potentially fight the beam and hurt the player, so it is best to immediately shoot them away, which disintegrates them.
- The name "Forgotten One" may be derived from the fact that Doom 3's Lost Soul has a new appearance. The shape of the Forgotten One, and thus the original Lost Soul, was "forgotten," so to say.