Allomancer Jak and the Pits of Eltania (2014)

Allomancer Jack and the Pits of Eltania is a fantasy short story written by American author Brandon Sand-erson as part of his Mistborn series. It was released in 2014.

Summary
The story starts with Jak waking up in a cave, out of metals. He then escapes the cave by jumping into the river in the canyon below after licking a tin deposit on the wall of the cave. He is promptly recaptured by the Koloss who want to make him their leader and a Koloss. He discovers that his girlfriend Elizandra Dramali is Koloss blooded. He does not want to become a Koloss, so he says that he already is one and will prove it by getting the Survivor's treasure from the bottom of a spear-shaped pool. He dives down, finds a chest, and brings it back up. It contains a number of Koloss spikes. The Koloss are so excited to have new spikes to increase their numbers, Jak and Elizandra manage to escape, and Jak realizes that the chest itself is made of precious aluminum.

Postscript
"This story is inspired by an idea of Brandon's brother Jordan, who wanted to do a radio drama, scripted by Brandon. The character Jak is meant to be in contrast to the more genuine, serious character of Wax, like the Adam West Batman versus the current Batman. Unlike The Eleventh Metal, this story is meant for established readers of the Mistborn series, revealing how Koloss are made in the post-Catacendre era.

-postscript from Arcanum Unbound

Publishing
It was originally published with the Alloy of Law rule book, an extension of the Mistborn Adventure Game. It was later released in part on Sanderson's website. It was also included in Arcanum Unbounded.