The Lost Soul was first introduced in Doom's second episode, The Shores of Hell, but can be seen as early as E1M1 on the PlayStation and Saturn ports of the game where they can be spawned by a Pain Elemental hidden in a secret corridor.
Doom II made additional use of the Lost Soul by utilizing it as the projectile attack of the new Pain Elemental monster. The Doom manual gives this description of Lost Souls: "Dumb. Tough. Flies. On fire. 'Nuff said."
- In a ZDoom-based source port, if the player is killed by a Lost Soul (monster is credited with delivering the blow that reduces player's health to 0%), an obituary message is displayed at the top of the screen: "[player name] was spooked by a Lost Soul". This obituary is used whether the Lost Soul was originally on the map or was generated by a Pain Elemental.
- In Brutal Doom, Lost Soul flames were removed from their sprite and are now generated by particle emitters. They now float in air and attack much faster and more accurately, specially in moments in which the player is busy switching or reloading weapons. They also "sidestep" a lot to avoid non-hitscan attacks - such as rockets, plasma and even the wind-up moment of the minigun - and retaliate with their own attack right after. They also tend to rapidly retreat all the way whenever the player tries to get physically close to them. All this plethora of rapid movement can cause slow or unlucky players to miss attacks constantly and expose themselves to quick retaliation, making them one of the most frustrating enemies in the game. They emit sparks and tiny bone fragments when hit, and do not bleed anymore. They still explode in flames when killed, their charred bone chunks fall to the ground (in v20 they were given the death sound clips from their Doom 3 counterparts). Berserk-powered players can punch (primary attack key only) Lost Souls in order to pick them up - they can be thrown like projectiles at other monsters (primary attack key again) or crushed in the player's hand (reload key).
In Doom RPG, the Lost Soul appears as a class of monster. There are three variations, identified by color:
Lost Souls can move three panels in a single turn instead of one, and will attack automatically once they are in an adjacent panel to the player, even if it has already moved. It attacks three times consecutively and can be damaged by the fire extinguisher.
- The Lost Soul is the only monster in Doom to not make any sound when alerted.
- The Lost Soul is one of two monsters that do not leave a corpse (the other being the Pain Elemental).
- Lost Souls appear in the Diablo franchise, similarly appearing as floating skulls.