This is the Chaos Dwarf WFRP supplement, originally planned for WFRP 1st edition and updated by the original author for 2nd ed. It falls within what I would consider our apocrypha, being written by GW authors but never officially released, putting this on similar footing to the Tuomas playtest.
Even though much of this contradicts later lore it is invaluable in providing the kind of fleshed-out world you get from the RPG side of Warhammer, as well as giving plenty of ideas for your own homebrew units, adventure hooks, and writing prompts.
WIthout further ado I present: Mad Alfred’s Chaos Dwarfs: From The Darkness