Plot summary
The protagonist is a human named Theodore, a 13th-century crusader who was sent to Limbo after his death at Jerusalem's wall.
He is led to play what seems like an old arcade game called Pony Island. It is revealed the game was created by Lucifer, who wants the protagonist to surrender his soul.
He is eventually contacted via an instant messenger program by Hopeless Soul. They instruct the protagonist to delete three core files (guarded by demonic entities Azazel, Beelzebub and Asmodeus). By doing so, Theodore is able to set the trapped souls free.
At the end, Hopeless Soul talks directly to the player and asks them to delete the game file.
Credits
Adapted from Wikipedia contributors, Pony Island. Section headings and formatting adjusted.