From Lexicanum

Captain Cato Sicarius from the Second Company of the Ultramarines was the commander of all Space Marine Forces during the Fall of Medusa V. He was armed with a pair of Lightning Claws. It was indeed he who led a coalition of his fellow marines from other chapters onto the dying planet in a heroic personal quest to neutralise the threat posed by the infamous Black Legion sorcerer Ygethmor, swearing an oath to slay the sorcerer with his own hands.

Among the chapters Captain Sicarius led, were the Dark Angels, Imperial Fists, Howling Griffons, Black Templars, Blood Angels and the Space Wolves.

At the conclusion of the Medusa V campaign, Sicarius sent the following message:

++Priority Transmission: Coding/Omega/Green++
++Recipient: All Adeptus Astartes Vessels – Medusa System++
++Subject: Courage and Honour ++
++Author: Captain Sicarius++

Brothers,

Leading the combined forces of the Adeptus Astartes on Medusa V has been a singular honour. In the name of the Emperor and our Primarchs, we have denied this planet to the arch-enemy and crushed the foes of Mankind.

Our losses have been grievous and at times hard to bear, but through it all, we have fought with the skill and dedication for which we Adeptus Astartes are known.

Already our Astropaths have received word that we are needed elsewhere, so our extended brotherhood must now part ways.

Courage and honour, my brothers – for the glory of our Primarchs and the Emperor of Mankind.

Cato Sicarius

++Transmission Ends++

Sources

• Codex: Space Marines (5th Edition)
• GW Medusa V website
• Source for Sicarius' First Name Cato (German)
• history extracted from the Medusa campaign section of WD317