Do you mean the item to upgrade your vanguards? You can get such items from defeating enemies or opening chests in the vanguard battles, and by fighting with them in the arena.
no, the one that allows you to craft legendaries using disassembled items. ah sorry i posted the wrong name. I meant this one. 
Edit: I still haven't found it.
Edit 2: by the way I kind of noticed that every time i do Ice raid then go to Fire raid the Autosave suddenly turns ON even though I already turned it off. Idk if it is also the same with the other people.
2 years ago(+1)
The dusty crafting book fpr the legendary item can be found in a chest in the fire raid area, which only appears after you won a solo fire raid. (Solo raids unlock after you've won enough fire raids with the raider group)
The auto-save is disabled during the fire and ice raids, as it is not intended that a save is created during the on-going raid events. It's not intended that the auto-saves is turned ON if it wasn't active before the raid, but maybe something went wrong. I'll take a look at it.
