Lucifer Gets Demoted
Dominus turns out to be both a machine and a disappointment. The X-Men fly to Lucifer’s new secret lair to discover that his race has spent a decade plotting to enslave mankind. Just so we know they’re serious this time, they have a huge machine and many giant robots. Issue 21 is basically a retelling of the Sentinels story with a villain that already sort of looks like Magneto.
The Dominus machine is a tower that rises from the Earth and emits rays that remove free will, reducing all intelligent life to domesticated slave labor. The evil alien race behind this plot has sent Lucifer to oversee the project. The machine itself is operated by green robots that are a lot like Sentinels.