The Volcanic Vault of the Forge Father

In ages long past, the Dwarven Sorcerer-Priest Hargen the Seven-Crowned stole a fragment of the Elemental Plane of Fire. Using this stolen power, he built a hidden vault deep within the earth. A volcano formed around the Shard, and in his volcanic vault, he forged many  great and terrible weapons, to war with the Gods themselves. However, exposure to the raw power of the Fire Shard corrupted the dwarves, twisting them into ferocious Ash Ghouls. With the last of his power, Hargen sealed the vaults. However, recent volcanic activity has caused the tunnels to reopen, and eager adventurers are taking the opportunity to plunder its depths before it is drowned in lava.

Use this (mostly) system agnostic adventure with the TTRPG game of your choice.  This was my entry for the One Page Dungeon Contest 2021, and I hope you enjoy it. One quick note that may not be clear: the "map" that's presented in the document is meant to be read as side view, to show the relationship of the floors to each other and two the deadly lava below!

Cover art: Pierre-Jacques Volaire, The Eruption of Vesuvius, 1771. Art Institute of Chicago.