I'm getting ready to head to Threshold in the hopes of completing the secret ending, but I've realized my crystal count is off. I have one from Areshkagel, one each from Deskari in Iz and Baphomet in the Abyss, and the purple stone knife. I know I will get one more each from Baphomet and Deskari during the final plunge, but I'm missing the one I initially dug out of the mine in the Nexus. How to I get the last stone so I can get everyone (including Areelu) to ascend?