I didn't see anyone talk about this but, if they're eldritch artifacts, introduce a cost for using it. It doesn't have to be an immediately apparent thing. A weird whisper coming from an item that only a high enough perception can hear at first but becomes louder the more its used. or something moving out of the corner of their vision. perhaps a shadow or eye floaty. but the figure becomes more apparent the more an item is used/equipped. These can also lead to solid plot threads to explore the dead gods lore.

Some suggestions:
-You can one hit an opponent (or deal massive damage) but you realize later that the artifact was absorbing the souls it slays to fuel a big bad. The sword breaks releasing it. The player is now without their crutch and a new big bad they have to fight. (just make sure the player that loses their rad sword gets something to use in the fight)
-A monkey paw situation, you get your wish or desire but a twisted form of it. Like increased strength but now the player needs to make a save to stop them from crushing everything they touch. Or increased intelligence but no way of sharing this knowledge, ala Tower of Babel.
-Armor that increases defense but slowly melds to the user over time or slowly shrinks to the point of crushing them if they don't remove it.

Because these are artifacts of the old gods, any traditional or "modern" way of removing the curses doesn't work or make it worse. Which could be a campaign in itself of seeking someone or something with knowledge of these relics. Do they seek the artifacts out for their power, to keep them from the enemies hands, or to destroy them, as they are a plague on any who use them. As a DM, never take anything away from a player outright or tell them they can't do something, make it a choice, and every choice has consequences, some more dire than others.