The Emerald Highway, so called for its brilliant green glow in the sunlight, is a marvel of engineering. Since making clouds takes vast amounts of water, the people of the Kingdom of Storms have come up with an aqueduct to bring a constant supply of spring water to their Cloudforges. These massive waterways just happen to be large enough to carry ships above the jungle.
During the construction of the highway system, there was a landslide and many lives were lost. The Immortal King of Storms made a great offering of solidarity and grief to those who had died; He offered up his own arm. His followers, having built many reliquaries, had never had such a momentous relic given to them before. They decided this relic would need a most magnificent temple, and they constructed a towering stupa at the site of the landslide memorial. The temple is a convenient pilgrimage on the Emerald Highway, and receives a constant flow of devotees.
The God-king's arm of course, grew back shortly after.