One of the many demons born from the Chaos Flame, the Old Demon King is now among the last of the dying race still existing in the world. It resides in a large chamber surrounded by the corpses of Capra Demons , Stray Demons and a Centipede Demon.
The Old Demon King was one of the many demons born from the Chaos Flame, and according to its soul's description, was the last remaining demon to have been alive before the Chaos of Izalith was extinguished, making it one of the oldest living beings in existence by the time of Dark Souls 3. After the destruction of the Bed of Chaos, the line of demons began to decline with no means of maintaining it. In spite of this mass extinction, the Demon King persisted until the events of Dark Souls 3, along with the Demon in Pain and Demon from Below (one of which will be reborn as the Demon Prince before ultimately dying). With the Chaos Flame extinguished, it has slowly withered away. When the King's health falls low enough, its inner fire will extinguish and it will kneel over helplessly, gasping and exhausted, perhaps hinting at its truly ancient age.
The Old Demon King is a relatively straightforward opponent with a slow and well-telegraphed moveset. It will alternate between melee swings of its great hammer or breathing a cone of fire directly in front of it, both attacks can be evaded by moving behind the boss. The player should beware of its flame wave attack which will create a ring of fire that travels inward towards the demon, sprinting away from the boss is recommended rather than trying to evade through the ring as it will often stagger the player out of invincibility frames.
The Old Demon King will often ignite itself in flames, adding fire damage to its melee attacks. Luring the boss into the small water pools around the area will extinguish its flames although it will attempt to reignite itself shortly afterwards. The mounds of demon corpses littering the area can be used to hide from the boss in order to use items although they will not block the flame wave.
If the boss begins to wave its hammer, it will summon a meteor shower. Again the corpse piles will block against the meteors although it is advisable to focus the camera above the player in order to track them. It can be staggered out of this attack although it is safer to take cover.
When the Old Demon's King's vitality is below 20%, it will collapse and start charging one final AOE blast. This feint is designed to lure the player close to it at which point it will release a large explosion, dealing a large amount of damage. This attack will permanently extinguish the king's flames and cripple it for the remainder of the fight, forcing it to slowly drag itself towards the player and a single hammer swing. As long as the player can survive the AOE blast, finishing off the boss should not be a challenge.
Great Swamp Cuculus: Her summon sign can be found near the staircase leading to the boss arena.
Knight Slayer Tsorig: If the player defeated Tsorig as a Dark Spirit in the Catacombs of Carthus, he can be summoned to help with this boss fight. His summon sign can be found near the Demon Ruins Bonfire (Defeating him again in the Smouldering Lake does not negate this).
Soul of the Old Demon King
- Weak against Black Knights' weaponry (Black Knight Sword, Black Knight Greatsword, Black Knight Greataxe, Black Knight Glaive).
- If the player defeats the Old Demon King with the help of Great Swamp Cuculus, a corpse will appear in the Undead Settlement, where Cornyx was originally found, containing Cornyx's Set and the Spotted Whip.
- The Demon Kings' appearance slightly changes throughout the fight, as he gradually becomes brighter until he performs his area-of-effect blast, after which his appearance will drastically change, with him now being flameless, frail, and crumpled looking.
- According to the item's description, the Old Demon King's great hammer is imbued with remnants of the Chaos Flame.
- The body of the Centipede Demon can be seen lying among the many demon corpses surrounding the boss arena.
- During the second phase of the fight, a slightly remixed excerpt of the Bed of Chaos's theme can be heard.
- Soul of the Old Demon King description.