If you Transmute an artifact, where all artifacts been spawned, it creates a ring instead. And that¨s fine.
The issue is that even a +10 artifact becomes a +0 ring, it seems a bit harsh, and it would have been nice with preserving some of the effort you invested in the artifact.
I can see some reasoning behind not having upgrades, as upgrades are a limited resource, carefully balanced, while certain artifacts cen be upgraded fairly quick. I therefore just ask to consider a modest upgrade, scaling perhaps 0…2, or a maximum of 0…3.
Considering that you only run into this problem once all artifacts have been discovered, you’re most likely already way past floor 15 to 20, of where a +2 or a +3 ring really shouldn’t cause too much issue with the balancing. Compared to what’s happening with Wealth farming, this is a minor thing.
Personally, I think a failed transmutation would have been better. I think it’s very rare to get a useful ring +0 when you’re probably at the end stage of the game.