"It is insufficient to cleanse world after world of the malefic taint of creatures such as these Tyranids. The dark void itself must be stained with the blood of this menace. It is not by the guns of the Imperial Guard or even the might of the Astartes that this will be done, but rather by the proud ships of the Imperial Navy."
- —Lord Admiral Anastasia Arkelius
She is a member of the so-called "Triumvirate" comprised of herself, her older brother General Derian Arkelius and Lord Commissar Vance Theren that collectively commands the Orpheus Salient of the Achilus Crusade following the death of General Mikal Curas to Hive Fleet Dagon.
The younger of the Arkelius siblings in Imperial military service, Anastasia Arkelius, a member of the noble House Arkelius on Scintilla, the capital world of the Calixis Sector, has enjoyed a more successful career than her older brother, General Derian Arkelius, having reached the higher ranks of the Admiralty while still only in her first century of life.
She is also an excellent tactician, albeit in naval engagements, but she commands the respect of her crew and the captains of her fleet. Those that serve her understand that while their souls may belong to the God-Emperor, their lives belong to her.
At the beginning of the Achilus Crusade, she served as a Rear Admiral, newly promoted, overseeing the movement of vessels through the Jericho-Maw Warp Gate and liaising with the Battlefleet Calixis Admiralty to maintain supply lines.
Placed in command of the six Imperial Navy battlegroups of the Orpheus Salient -- Icarus, Argo, Cerberus, Daedalus, Vishnu and Santos -- she was shortly thereafter elevated to Lord Admiral and commander of all Imperial Navy forces within the salient.
Being a fine tactician and a responsible commander, Arkelius understands the weight of command well, and the burdens of the Admiralty are great indeed, with the lives of hundreds of millions of souls on thousands of ancient, venerated and often irreplaceable starships, within her hands.
Arkelius' flag can be found within Battlegroup Cerberus at present, as it has been since just before General Curas died. It operates close to the Iron Collar, and part of the group was anchored above Hethgard until the Tyranids reached that Fortress World.
From the battlegroup, Arkelius commands the other four remaining battlegroups (Battlegroup Argo having been lost with General Curas) as best she can, given the difficulties of communicating through the Tyranids' Shadow in the Warp and the scattered nature of those battlegroups due to withdrawals and defeats.
When General Curas was lost, and Lord Commissar Theren wrought his deception that the general remained alive if missing, Lord Admiral Arkelius was the first to be informed and brought into what would become the Triumvirate that now commands the Orpheus Salient.
To this day, she uses that, and the swiftness of her ascendance to one of the highest ranks in the Imperial Navy, to taunt and bait her elder brother into some rash course of action, maintaining a rivalry that has existed between them since they were children.
She hopes that in this way she can provoke him into doing something that will eliminate him from being chosen as General Curas' successor to command the salient.
That she is still willing to antagonise her brother, who is the most powerful Astra Militarum commander in the salient and extremely valuable to the continued conflict there, demonstrates perhaps her greatest flaw in judgement, placing a long-standing family feud and her own pride above the defence of the salient's remaining worlds.
Without Lord Commissar Theren to mediate disputes between the two, the Orpheus Salient might have collapsed entirely years ago.
As is common amongst the officers of the Imperial Navy, Arkelius regards the Adeptus Astartes with a mixture of caution and respect. Few officers in the Navy feel comfortable with the Space Marines maintaining their own fleets, and an uncertain peace exists between the Navy and many Space Marine Chapters over the matter of war-fleets. However, Arkelius respects the Space Marines' prowess and effectiveness, though she is cautious of their ulterior motives.
With the Deathwatch, the same is true, though to a greater extent, and she is far from appreciative when her vessels are commandeered for clandestine and sometimes near-suicidal missions.
- Deathwatch: The Achilus Assault (RPG), pg. 142
- Deathwatch: The Jericho Reach (RPG), pg. 136