Pain elemental

Pain Elemental is a monster in Doom II. Similar to Cacodemons they have a single eye, float and have a large mouth. However Pain Elemental's also have tiny arms which aren't used for very much. Instead of shooting a standard projectile, Pain Elemental's shoot Lost Souls. Because of this, they will never be targeted by another monster, though it is possible to have them target another monster (which is useless anyway since the Lost Soul doesn't inherit the Pain Elemental's target). In Vanilla Doom, Pain Elemental won't shoot Lost Souls if there are already 20 or more of them on the level.