This has the nasty effect of causing the second artifact found to override them all.
Natural artifacts are unaffected, they appear to be assigned id in the format of artifact_0, artifact _1, artifact_2, and so on.
When a second artifact is encountered in game it is fine, but once the game is saved and the artifact file updated and reloaded, all non-Natural artifacts are the same. Only the charges an item had is saved. Each time a new non-Natural artifact is found, it overwrites all existing artifacts due to this id conflict, and in the artifact file, each entry is simply replaced so you have 5 copies of the same artifact, for instance.
I have made a mistake. ALL artifacts suffer this. I looked at the code and couldn’t figure out why non-natural would only be affected. The truth is all artifacts are. However, in the stable 0.A release, artifacts are given proper numerical progressing ID’s. I had collected two artifacts, updated to experimental, and all new artifacts were _zu, I just hadn’t picked up an natural artifacts since I updated.
I downloaded the latest experimental (Windows SDL Build #1284) 0.A - 385825e and the problem still exists. It seems that _%zu is not functioning properly.