The boss of Old Hero Archstone.
The Storm King is an oversized storm beast with a large multi-spear attack which homes in on the target's location.
"After purification, heroes' remains are offered to the Storm King. His wings cover the sky, and he is accompanied by Storm Beasts."
The Storm Beasts are one of the objects of worship of the long dead Shadowmen. They believed the beasts brought forth the rain and came from / were ruled by the God Storm King. Storm Beasts resemble flying stingrays, have two eyes, and are very physically weak. When they spot the player they will inhale a large puff of air to propel a quartz spear, made from their marrow, to impale the player. They are somewhat sadistic and take delight in seeing men in peril. At the exit of the first Reaper chamber is a mound of dozens of slain Storm Beasts, this implies that the Reapers are using the souls of the Storm Beasts to summon Shadow Lurkers and reanimate Skeletons.
Storm beasts are the only source of cloudstone, a green ore that blocks light and blunts magic damage. It is said to come from the sky, but it is unknown if this is literal (as in the ore is collected by the storm beasts as they fly around) or if cloudstone is just a part of storm beast anatomy (their bone, minerals crystallized in their stomach, etc.).