This is the spot where a young adventurer met the hungry jaws of some unknown beast. There isn't much left - just a tattered pointy hat and a Mage's Staff. It couldn't save this poor soul, but perhaps it will do better in your hands.
The Mage's Staff is a magic hero's best friend in the beginning. Even though the price is big and the artifact uses both the Right and the Left Hand slots, it reduces the casting cost of all spells in a stage when heroes have little mana. However, as soon as the hero improves the mana pool and recover rate, the Staff becomes just a waste of slots. Then, it is better to remove the Staff and equip better artifacts instead.