Kallarn Lo'Vosh
Gaidin
Ok so Bands of Mourning came out and now there's this. Going by what I read its a companion story to the Original trilogy but has major spoilers for those and spoilers for BoM. Never even heard of it before today!
https://www.reddit.com/r/Mistborn/comments/42o8aq/mistborn_secret_history_explanation/
http://www.amazon.com/Mistborn-Secret-History-Brandon-Sanderson-ebook/dp/B01B0NS93U
https://www.reddit.com/r/Mistborn/comments/42o8aq/mistborn_secret_history_explanation/
http://www.amazon.com/Mistborn-Secret-History-Brandon-Sanderson-ebook/dp/B01B0NS93U