I'm currently working on a little homebrew adventure and was wondering what would be some rare/important raw materials that the Imperium would be interested in enough to hold an interest in a planet but not so rare as to validate sending in the Imperial Guard if the flow of these resources were halted or disrupted?
My first thought was some kind of metal, perhaps adamantine or something similar but wanted some more input from those that might know more.
I need it to be something that could be gathered by feudal society but still important enough warrant a team of acolytes