The land of Boletaria is plagued by a colourless fog that unleashes a terrible demon, the Old One, which was sealed away eons ago. The Old King Allant's awakening sets off a chain reaction of terrorizing mankind. A lone hero must save Boletaria from its doom.
Demon's Souls is an action role-playing game where players can choose from various starting classes, including hunters, knights, soldiers, priests and magicians. The objective is to progress through five worlds and defeat demon bosses at the end of each level. Killing enemies earns souls, the game's currency, which can be traded for weapons, spells, miracles, items and equipment or used to upgrade stats at the Nexus, the world's central hub.
During combat, players must monitor the protagonist's stamina bar, which decreases with physical movements like attacking, evading or blocking. Death does not end the game; instead, the hero respawns in soul form, losing health but increasing damage output against foes. Each death results in lost souls, which can be recovered by touching the spot where the character died.
The game features an online component, allowing players to observe others playing in "alternate universes", running around levels as white phantoms. Players can also leave messages about dangers like strong enemies or traps on the ground, which other players can read. Special items enable cooperative play with other players or invading their worlds to kill them.