I am trying to find out how vulcan died but i cant find it anywhere. I also would like to know any other "obscure" fluff for the salamanders.

I know most things about them
They are from Nocturn not Prometheus
Vulcan, thier primarch is dead
Each company rules over a city state on Nocturn
The only company to reside on Prometheus is the 1st Company Firedrakes
The world of Nocturn has the horrible Time of Trial that lasts 5 years
The salamanders make their own equipment
This gives their techmarines time to create masterwork items
Most salamanders self incarserate themselves if neccesary

That is the outline, i know a lot more, but the question of vulcans demise i cannot answer. Thank you