The Blinding of Ioun

Ioun often used her powers of prophecy and foresight to thwart the actions of other powerful entities. It seems at least one of them took issue with this; Ioun was attacked in one of her own temples.
While Ioun wasn't able to foresee the assault itself, some action tipped her off very early in the proceedings. She was able to call others to her aid and survived, but ended up blinded. As a result, many of her most powerful faithful are ritually blinded. Some end up blinded when they look into the future, but if the faithful of Ioun know who's responsible it's not publicly known. It is commonly surmised that another deity was involved since deities are immune to mortal weapons.