Io Guardian costs 300 gold and 25 favor, and decreases special attack recharge time by 20%.
Tale of the Dragon
With patch 2.7, Io Guardian costs 300 gold and 15 favor, and decreases special attack recharge time by 40%.
Zeus transformed his lover Io into a white cow to protect her from the wrath of his jealous wife Hera. But Hera saw through the ruse, and requested the cow as a gift. She then sent her servant Argus, a giant with a hundred eyes, to guard the cow. Eventually, Zeus sent Hermes to trick and slay Argus. To honor the memory of her fallen servant, Hera placed the eyes of Argus on the tail of the peacock.
Io Guardian original icon from the Age of Mythology pamphlet