Conversation so far:
what was imperial by Cassandra Nova?
Angered at Cassandra Nova's treachery and realizing the danger she posed, the Imperial Guard fought Cassandra, who defeated them and headed into the mansion.
what was the imperial guard for with Cassandra Nova?
The Guard with Cassandra Nova fought the X-Men until they were able to show the truth to the Imperial Guard.
was this successful when the Guard fought the X-Men until they were able to show the truth to the Imperial Guard?
Cassandra Nova's essence entered the body and was locked into a self-repeating program in the synthetic brain.
what was Cassandra Nova's greatest accomplishment?
Now in Xavier's body, Cassandra Nova mentally forced the Xavier Institute student Beak to beat Beast into a coma after he discovered that Xavier and Cassandra shared the same DNA.
what else happened after Cassandra mentally forced the Xavier Institute student Beak  to beat Beast into a coma?
Cassandra Nova then contacted the Shi'ar, whose leader was Majestrix Lilandra, Xavier's lover. Cassandra manipulated the Shi'ar Imperium

Question: what is the most important fact mentioned in this article?
Self-contained rewrite: what is the most important fact mentioned in this Cassandra Nova article about Imperial?