| Lost soul | 
| Appearance: | s | 
| Health: | 20 | 
| Armor: | 0 | 
| Accuracy: | +12 melee (if its charge connects, see below) | 
| Melee Damage: | 4d3 = 4-12 = 8 avg | 
| Projectile Damage: | None | 
| Speed: | 120% | 
| Standard Depth: | N/A; doesn't naturally spawn by itself, but will start spawning in monster groups in A100/A666 on floor 30 | 
| Experience Value: | 68 | 
| Inventory: | None | 
| AI habits: | Uses items: | No | 
| Uses doors: | No | 
| Attack %: | 70% | 
| Special abilities: | This enemy flies, so it is immune to both damage and movement-slowing from fluids. Has 50% bullet and 75% fire resistance. | 
| Ingame description: | The flying bluish skull. Wouldn't be a problem if there weren't so many of these nightmarish things... | 
| Comments/special: | Leaves no corpse on death. Will run through any fluid to reach the player. Will not infight with other monsters. Normally has 120% speed, but will charge the player when it attacks, with its speed going up to 480% while charging. The player can dodge a charging Nightmare Soul, and when it charges it will keep flying in a straight line until it hits the player, another monster, or a wall. A Nightmare Soul will additionally stop charging if it is hit, or has traveled 15 tiles. |