I liked the artifact part of the Grave Robbers. I didn't like, however, the gaining of life. And they get rid of the artifacts. Sure, it could be implied they're selling that stuff they find. But you're a powerful planeswalker who is aware of magical items, no? If you dig up magical stuff, you might just want to use it!
Then I thought about how this doesn't have to be a creature. It shows the act of grave robbing, so this can be an instant or sorcery. Beacon of Unrest and Scrounge both show different black spells that get artifacts from the graveyard.
Graverobbing here is the pure form of the same effect, with no other twists, etc. This effect hasn't existed yet, in Magic: The Gathering, and it looks like this is a good place to do a spell like this. The name is applicable to any world so that it could be reprinted again in the future.