Complex sentence: There, he finds out that the N.O.V.A has stolen the Judger's artifact from Yelena, who is now transformed into a living human woman by Prometheus, the artifact of which could transform Earth back into the habitable planet it once was.
Split into simpler sentences: There, he finds out that the N.O.V.A has stolen the Judger's artifact. The artifact could transform Earth back into the habitable planet it once was.