Blackhole was a code name used in Palpatine's Galactic Empire. Its first user was Lord Cronal, former Prophet of the Dark Side, when he became Director of Imperial Intelligence. Following Cronal's death at the Battle of Mindor, the code name was inherited by Grand Vizier Sate Pestage, who co-opted this façade as a cover for himself while helping Palpatine return to power in a clone body and establish his Dark Empire.
Sources
The Star Wars Spy Game: SPIN Declassified on StarWars.com (backup link) (original link is obsolete)
The Imperial Warlords: Despoilers of an Empire: Part 3 on StarWars.com (original link is obsolete)