How to GetEdit
Unlike any other type of grist, Artifact cannot be obtained via strifing. Instead, it is acquired from alchemizing Sweet Bro and Hella Jeff-Tier Items, as they more often than not cost negative Artifact.
As mentioned above, Artifact Grist is more often gained from alchemizing instead of lost, so usually it's just a counter of sorts for how much SBaHJ-tier items you have alchemized. Sometimes, though, you may come across a SBaHJ-tier item which costs Artifact to create, meaning all the Artifact you have accumulated over time may actually be useful.