About Soul Stones
Soul stones can be equipped by monsters to increase their stats. A monster can equip only one soul stone, which can be replaced or dropped if needed.
You can gain a soul stone from any monster by destroying it. The monster will be gone permanently and will give a soul stone based on its element.
Soul Stone Guide
Air Soul Stone = +Speed
Water Soul Stone = +Magic
Fire Soul Stone = +Attack
Death Soul Stone = +Attack, +Magic
Earth Soul Stone = +Defense, +Resist
Life Soul Stone = +Defense, +Resist, +HP
Arcane Soul Stone = +Defense, +Resist, +Attack, +Magic