And it took you 5 minutes? :)
Had saved up a few artifact XP items and see that the tooltip for some mention that they will not increase XP if you increase your research level, but most of them did not have this text. I increased my research level.. and what do you know, none of them increased the XP gain. So the morale was: Use them immediately and get more free inventory space.
Unlocked the Training mission in the ruins today, they should come with a warning that it takes forever to explore all of it. Was saving up my withered guys so they could carry out the big 10 man chests, only to be ambushed by an elite that killed all of them. In the end I only managed to exfil with a 10 + a 5 man chest... so the morale was: If you have 11 and there's a 10 man chest around the corner, use them on it before they die.
And finally found out what the Mana would be used for.. since incursion into the ruins could cost up to 1400 mana to spawn with 14 or so withered.