The Artifact is a mysterious object forged by unknown hands for unknown purposes some unknown time in the past built from very well known materials.
DeathSpank: Orphans of JusticeEdit
DeathSpank spent most of his life trying to get to the Artifact, and by the time of the first game it was sealed in the Demon Mines by the Demon Witch Heybenstance (although she was paid by Sandy to do so). DeathSpank had to find ingredients for the Demon Witch so that she could create a crystal, that when fully charged with Demonic Rubies, could break the seal.
However, the Artifact was also protected by a monk and his two dragons, Ashley and Bubba. DeathSpank was able to slay the dragons and finally obtain The Artifact. Unfortunately, after leaving the mines, he was attacked and mugged by Sergeant Orque and his two lackies. They took all of DeathSpank's items, including the Artifact, which Sergeant Orque took to Lord Von Prong.
After killing Von Prong, DeathSpank reclaimed The Artifact, but Sandy stated that it wasn't important, after finding out that Von Prong had a thong not unlike the one DeathSpank wears.
DeathSpank: Thongs of VirtueEdit
The Artifact doesn't appear in the sequel, but is mention towards the end. Sandy reveals that The Artifact was worthless (and even states she got it for five dollars at a garage sale) and that it only served to test and manipulate DeathSpank. This is confirmed even further as there is a pile of "Artifacts" behind Sandy on the Moonbase.