Demon's Souls are obtained by defeating named bosses and are crucial for crafting unique weapons or learning powerful Magic spells and Miracles. Do not consume a boss soul if it's your first playthrough, as they offer significant strategic advantages when used correctly. Blacksmith Ed requires the Red Hot Demon's Soul before he can begin upgrading weapons with other Demon's Souls.
Unique Weapon Creation
Demon's Souls can be given to Blacksmith Ed to forge unique weapons. To unlock this ability, you must first provide him with the Red Hot Demon's Soul. After this, he can use other Demon's Souls to create powerful armaments.
Magic and Miracle Learning
Alternatively, Demon's Souls can be used to learn Magic spells from Sage Freke or Yuria, The Witch, and Miracles from Saint Urbain. This offers a different path for character progression, allowing you to enhance your magical or faith-based abilities.