if there was unique artifacts… or sets like in Diablo 2… equip 4 specific artifacts to 4 monsters on your team and get x bonus stats or a special team wide effect like first strike or immune to spells or something
The unique ones could have say and additional skill on it or something like immune to stun or status effects in general. Or maybe be able to have two legendary materials added… to prevent broken combinations they could come with one already on them but you could add one more
I think this would drastically provide more end game content. I would even be willing to come up with a few examples myself
Off the top of my head one unique could be
10 bonus enchant slots on top of of the ones gained from leveling the artifact and creature always attacks first.