Where do you get the upgradable artifacts?
 

which artifacts are upgradable and where are their locations?

Game engine is random so every time you start a new game items are randomized. However, some items are at fixed locations (eg. Kerus' Sword at Road Architect)
Some upgradable stuff:
1) Archimage Staff
2) Royal Snake Ring
3) Steel Boots
4) Pain Skull (it does have two levels but it can be upgraded only by fighting battles)

Are you listing the items as fixed items you can always get? If so, where do you get the Royal Snake Ring? I don't recall seeing it.

Another question, is the Demetrius sword a random item or are you guaranteed to get it somewhere?

Thanks in advance for any help.

Anyone who played through the game who knows? Is the Demetrius always offered at some point, or random? I'm trying to decide whether to switch to demons.

Thanks.

I'm pretty sure it is random, I think I've only seen it once in my three completed games. Very, very few item are guaranteed.

There is only one item that is fixed during the game course and available for upgrade - the adherent staff after completing the magic range in Arlania.