Maybe instead of a failure chance - write up a list of traits that that work with a powerful LE dragon, every time the artifact is used, the user gains one of those traits (no roll - just gains), examples:But I'll bite - okay so what could be an interesting consequence of failing? What would correspond to never being able to cast Wish again?
You can never take flight? Vulnerability to <s>poison</s>necrotic? It is hard to find a consequence that does not meaningfully gimp the character in regular play, yet means definite pain that cannot be trivialized.
1. User can no longer lie (known to never utter a lie);
2. User can no longer attack to subdue (was known to have no mercy);
3. User has the friends cantrip on all the time (sounds great until you read the downside) - known to have a silver tongue, but with a dark edge.
Same as above (put it on the list) - Use of the artifact will replace an Ideal, bond/and or give the character a dragony flaw.Getting your traits/bonds/etc replaced with entries from some lawful evil dragony table (if one exists) would be kind of cool. Maybe I need to check up on the various DnD indexes there is...