Skeleton

"The dark forces are economical and reuse dead bodies to make the world a better place! The Skeleton is an inexpensive yet effective foe." - Manual
The Skeleton is the most commonly seen enemy in the Demon Fortress and is probably the least intelligent. The Skeleton is worth 100 points.

Normal Mode
They have a set walking path and let you shoot them.

Hard Mode
Their difficulty is cranked up, because now instead of just walking they will occasionally stop and throw a bone which bounces around twice before stopping. This one change makes them a tremendously more formidable foe.

Hell Mode
The same as Skeleton's Hard Mode Behavior but much faster making this the ultimate version of the skeleton finalizing him as incredibly annoying and frustrating to play around.