Agate Mountain, before its collapse, was a mountain within the Claws of the Clouds range that was introduced in Darkstalker. It contained a small cave that imprisoned Darkstalker for approximately 2,000 years.
Agate Mountain was located to the far east of the lost city of night. It was the tallest mountain in the Claws of the Clouds range, and contained a small cave. It rested near Jade Mountain above several valleys, and was surrounded by small yellow wildflowers growing out of the dirt. The cave where Darkstalker was imprisoned ended in a small chamber, with solid granite on all sides. The entrance was filled with boulders by Clearsight, and the mountain was destroyed by an avalanche soon afterwards. Before its collapse, it was the tallest mountain in Pyrrhia.
In modern Pyrrhia, Agate Mountain has been reduced to a gaping maw in the earth, a mouth studded with rocks and drooling splintered trees. The crevasse goes too deep underground to see the bottom from the surface, and the walls narrow as the crevasse becomes deeper. From the bottom of the gorge, the light fades to a small strip of brightness overhead, and the stone is smooth and cold. It contains several outcroppings along the walls, as well as a small crawl space. All around the crawl space, there are hundreds of claw marks within the stone — some firm and bold, others tiny and slanted to fit in around the others. A discarded scrap of rusty metal wires lies near the opening, frayed and looped around a trio of misty white gemstones, along with a smooth mouse skull the size of a dragon tooth.
The Jade Mountain Prophecy
Peril accidentally released Darkstalker by burning his scroll. Darkstalker slowly rose out of the ground from his prison.
Darkstalker was released from his prison underneath the mountain at the beginning of the book.
Whiteout told Darkstalker that Clearsight had taken his scroll and wanted to meet him at the mountain. Clearsight flew away to Agate Mountain after Fathom had enchanted Clearsight's moonstone bracelet. Darkstalker and Clearsight met at Agate Mountain. Clearsight put the enchanted bracelet on Darkstalker's arm and imprisoned him underneath the mountain, filling the cave with boulders from the hills.