As a warrior and as a paladin, you may need a second artifact slot to boost your weakness (less mana, lower intellect, etc.) as well as work on the rune/stat items (ancient amulet or ring of mind class 2). In these cases, 1 artifact slot is not enough at all. Especially on impossible, where you need to be flexible all the time, Agvares and Elenhel can work wonders for you.
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