The Slayer of Demons is the player character and main protagonist of Demon's Souls.
In trailers, artwork and promotional art for Demon's Souls the Slayer of Demons is depicted as a male Knight, with the same equipment as the knight class.
In the game however, the Slayer of Demons' appearance and attributes are freely determined by the player, including sex, origin, tendency and equipment.
The Slayer of Demons has no dialogue and his or her personality depends entirely on the player.
The Slayer of Demons journeyed to the land of Boletaria in search of Demon souls. Travelling through the thick fog surrounding the land, the Slayer of Demons is guided to Boletaria by the Monumental, who wishes for the Slayer of Demons to lull the Old One back to slumber. The Slayer of Demons makes their way through the castle, defeating a Vanguard only to be slain by the Dragon God. They then awake in The Nexus, a place where the souls of the dead are trapped forever. They are saved by the Maiden in Black, an ancient demon, that tells them to seek the Monumental in the upper reaches of the Nexus. The Monumental proceeds to explain the origins of the Old One, the Demons and the Monumentals, and asks the Slayer of Demons to put an end to the scourge of demons by vanquishing as many powerful demons as they can, in order to get close enough to the Old One to lull it back to sleep. The Maiden in Black offers her services to the Slayer of Demons, possessing the power to channel demon souls. Through four Archstones inside the Nexus, the Slayer of Demons can travel to the real world and fight the demons.
The Slayer of Demons travels to the now ruined castle of Boletaria, which has become a haunt of soul-starved soldiers and a feeding ground for dragons. Here, the Slayer can encounter Ostrava of Boletaria, a would-be hero and the disguised prince of Boletaria. Ostrava will seek the Slayer's aid in reaching his father, King Allant. The Slayer of Demons makes their way through the castle, defeating the Phalanx and the Tower Knight before finding their way forward blocked by an impassable fog.
Returning to the Nexus, the Slayer of Demons proceeds to the Stonefang Tunnel, a giant mining complex whose stubborn miners, who once supported the soldiers of Boletaria, continue to mindlessly excavate ore, while the evil hidden deep inside the tunnel is allowed to fester. Here, the Slayer of Demons can encounter Patches the Hyena, who will attempt to lure them into a trap, only to claim innocence when said trap fails. The Slayer of Demons may also encounter Blacksmith Ed, a blacksmith of incredible skill and knowledge. Descending deeper and deeper into the tunnel, the Slayer of Demons battles the Armor Spider and the Flamelurker before finally facing off against the Dragon God once again. After having slain the Dragon God, an arch demon, the Slayer of Demons grows in power and leaves to find more arch demons.
Next, the Slayer of Demons travels to the Tower of Latria. Once home to a benevolent, magic-wielding queen, the Tower fell to demonic infestation after the queen's deposed husband returned home at the helm of a demon army and wearing a strange demonic garb. The king killed the queen, and imprisoned countless people in the tower, which became a place of torture and misery. The Slayer of Demons may encounter Sage Freke, a mighty magician caught unawares and imprisoned inside the tower, and Lord Rydell who was killed and whose spirit remains trapped in a cell. The Slayer of Demons may choose to free both men. If freed, Sage Freke will return to the Nexus and offer his expertise as a sorcerer, while Lord Rydell will reward the Slayer of Demons for helping him return to his body. The Slayer of Demons may also encounter Yurt the Silent Chief, an assassin working for Mephistopheles. The Slayer of Demons may rescue Yurt from his cell, causing him to resume his killing spree, or kill him. If the Slayer of Demons has taken enough lives themselves, Mephistopheles will appear to them in order to attempt to get them to replace Yurt in her service. After defeating the Fool's Idol and Maneaters, the Slayer of Demons may confront the Old Monk responsible for the kingdoms downfall. However, the demonic garb that had been possessing the Old Monk leaves him, summoning another to do its bidding. After slaying the garb's new servant, the Slayer of Demons leaves the tower, having slain another archdemon.
The Slayer of Demons now travels to the Shrine of Storms, home to the Shadowmen who care for the dead. The island shrine is now a ruin, home to skeleton soldiers possessed by the spirits of the dead and stormbeasts. Here, the Slayer of Demons may find Graverobber Blige, a graverobber who if freed from his cell will sell his goods to the Slayer of Demons, and also reencounter Patches the Hyena, who once again attempts to lure the Slayer of Demons into a trap, only to beg forgiveness. The Slayer may also encounter Saint Urbain, a miracle worker who was also fooled by Patches. If rescued, he will return to the Nexus and share his knowledge of miracles with the Slayer of Demons. Finally, the Slayer of Demons may also encounter Satsuki, a strange warrior that seeks the Magic Sword "Makoto". After defeating the Adjudicator and the Old Hero, the Slayer of Demons will face off against the Storm King, a giant stormbeast. The Slayer of Demons may use the magic blade known as Stormruler to vanquish the beast, and return to the Nexus having conquered another archdemon.
Finally, the Slayer of Demons travels to the Valley of Defilement, a place of death and disease where the unwanted and forgotten live. Some time ago, the Maiden Astraea and a contingent of holy knights travelled here to purify the valley. However, the maiden fell to corruption and became a demon, while her party of knights perished in the swamp, with the exception of her childhood friend and protector Garl Vinland, who remains by her side. Here the Slayer of Demons may encounter Selen Vinland, the sister of Garl Vinland, who has come to seek her brother in order to deliver their fathers' dying words to him. She will ask the Slayer of Demons to help her find her brother. After defeating the Leechmonger and Dirty Colossus, the Slayer of Demons will be face to face with Astraea and her protector Garl Vinland. Astraea will ask the Slayer of Demons to leave them in peace, telling them there is nothing for them to plunder there. However, the Slayer of Demons will not relent, and will either slay Astraea, leaving Garl Vinland without the will to live and causing him to become a fearsome black phantom, or slay Garl Vinland, leaving a defenceless Astraea to commit suicide.
Return to the Boletarian Palace Edit
Now finding the fog blocking their path lifted, the Slayer of Demons proceeds deeper into the palace. Now they may rescue Biorr of the Twin Fangs, a Boletarian hero and loyal defender of the king, and Yuria the Witch, who will offer to teach her witchcraft to the Slayer of Demons, if they are willing. The Slayer of Demons may also continue to aid Ostrava of Boletaria. If they help him all the way, he will confront his father and learn the truth, proceeding to give the Slayer of Demons a key to the mausoleum that holds Old King Doran and the sword Demonbrandt before killing himself, appearing shortly thereafter as a fearsome black phantom. After defeating the Penetrator and making their way past the terrifying Blue Dragon, the Slayer of Demons may finally confront Old King Allant, the man responsible for the demon scourge and the awakening of the Old One. After defeating the king, who is revealed to simply be a demon fashioned in the king's likeness, the true king speaks to the Slayer, telling them to seek him out.
The seal of the Nexus is broken, and together with the Maiden in Black, the Slayer of Demons travels deep below the Nexus to confront the Old One. The Old One welcomes the Slayer, who enters it to find the true King Allant, now mutated and corrupted by his immense power into a shapeless blob. After slaying the king, the Slayer of Demons may claim his blade, Soulbrandt, and is faced with a choice.
• Lull the Old One to sleep: In this ending, the Slayer of Demons will fulfil their task and allow the Maiden in Black to lull the Old One back to slumber. As the Slayer of Demons walks away, they see the Old One and the Maiden vanish into the fog. The fog would then recede, ending the demon scourge. All the souls lost in the scourge would never be reclaimed, but the fragile world now had a new Monumental to watch over it. One of unprecedented power; the Slayer of Demons.
• Serve the Old One: In this ending, blinded by their thirst for demon's souls, the Slayer of Demons strikes down the Maiden in Black and steps over her corpse to go deeper into the Old One. The Old One sensed a new and powerful demon by its side, and before long, the world would be engulfed by the Deep Fog as the Slayer of Demons sought ever more souls.