Cores are primarily used in the creation of scrolls by scribes, however cores can be used (1 core per item) in armor to increase an armor's resistance to a particular element as well as lower it to its weaknesses.
Core of Flame : Dropped by Fire Elementals - Used in inscription
Core of Earth : Dropped by Iron Elementals - Used in inscription
Core of Nature : Dropped by Nature Elementals - Used in inscription
Core of Flame : Dropped by Fire Elementals - Used in inscription
Core of Earth : Dropped by Iron Elementals - Used in inscription
Core of Nature : Dropped by Nature Elementals - Used in inscription