|It completely protects its wearer from the effects of clouds.|
Cloud immunity is an ego which protects the wearer from the effects of all clouds in the same way as Qazlal. It can only be found on the robe of Clouds.
Note that some cloud-generating breath weapons deal impact damage when they hit you; cloud immunity does not protect you from this damage, or statuses directly from that damage. Examples of this include catoblepae's Petrifying Cloud, swamp dragons' Poisonous Cloud, and ushabtiu's Death Rattle.
Cloud immunity is fairly niche overall. It allows you to use clouds from the Freezing Cloud spell or scrolls of poison without harming yourself, making them much easier to use. However, this should be weighed with other, alternate armour options, such as troll leather armour and swamp dragon scales.
Cloud immunity is especially useful in the Swamp, where the two main poison threats (swamp drakes and swamp dragons) only poison you through clouds, and ghost crabs also have a cloud attack. It may also be useful in the Volcano, the Ice Cave, or the occasional vault that generates hazardous clouds.