Iridescence[]
Name given by SE to the "hidden effect" of the elemental staves. It increases the effects that weather bonuses give by +10%; there is a penalty to magic aligned with the opposite weather of -10%. This is applied independent of the normal weather bonus, greatly increasing your chances of a 10% bonus and allowing for a 20% bonus. If paired with Elemental Obis the bonus of both effects is forced, creating a 20% bonus under the correct weather.