From Warhammer 40k - Lexicanum
The Hrakon Campaign was fought by the Dark Angels during the Nova Terra Interregnum.
During the conflict, the Inner Circle directed the Dark Angels to seek out Obidiah Hrakon, the despot ruler of an upstart planet and key rebel supporter of Nova Terra. In the Veiled Region, the Dark Angels finally cornered Hrakon, who took refuge on a pirate port world. Seeking to ensure no escape, the Dark Angels fleet blockaded the planet and unleashed the entire Deathwing via teleportation. Slaughtering all before them, only Obidiah, now revealed as a Fallen Angel, still stood. Refusing to give up, he was subdued in a duel with the Master of the Deathwing and was transported back to The Rock.
- 1: Codex: Dark Angels (6th Edition) pg.36-37