This item has been removed from the Aether mod and there are no news of it being re-added back into the mod. The Cloud Staff is a dungeon reward found in the Aether. When right-clicked it summons two Cloud Guardians who fly beside your head. Every time you right-click, the Guardians will each fire an ice ball at your target doing 2.5 hearts of damage per ice ball. The Cloud Staff can be used 61 times before breaking.
The ice balls fired by the Cloud Guardians are identical to the ones fired by the Sun God, but cannot be used to kill that boss.
When the Cloud Guardian is inside a wall and you right-click, the ice ball can hit you.