Allomancer Jak and the Pits of Eltania

Allomancer Jak and the Pits of Eltania is a short story about an adventuring Allomancer named Jak, as told by him and edited by his Terrisman steward, Handerwym. Handerwym's annotations imply that the narrator is unreliable (prone to exaggeration and ignorance), but we do find out some information about koloss society post-Catacendre. It was originally published with the Mistborn Adventure Game's extension Alloy of Law, later released in part on Sanderson's website, and also included in Arcanum Unbounded.