Herqilius Arstyn was a male Human officer of the Republic Navy during the New Sith Wars. He was widely considered, by civilians, soldiers, and Jedi alike, one of the finest Republic officers and best commanders of his era; his reputation began early in his service, when he was selected for the Republic Naval Academy on Prefsbelt IV and an extra year of advanced training at the Republic Navy War College on Anaxes. He repeatedly defended the Perlemian Trade Route against assaults by the New Sith Empire, and was something of a nemesis to the Sith Overlord Darth Saleej. After winning a particularly harrowing battle at Lantillies, he was nicknamed "the Bulwark of Lantillies". Such was his fame that even Jedi Initiates at the Jedi Temple on Coruscant had heard of him. Arstyn himself respected the combat prowess of the Jedi Knights, though he was less than thrilled with the succession of Jedi Masters serving as Supreme Chancellor.
In 1,389 BBY, Arstyn planned a punitive expedition into Sith space, hoping to turn the war by forcing the Sith onto the defensive. To defend his homeworld, Gizer, in his absence, he sought an alliance with the Gray Jedi Karr Shadeez, who had won notoriety for his own campaigns against the Sith and the uncanny success of his forces. At the same time, the Council of Five continued to seek gains on the Perlemian. Having recently failed to assassinate Senator Glavial Iltek on Taanab, the Sith Acolyte Alecto offered to assassinate Arstyn instead, and her Sith Lord master, Nerlus Zedum, elected to give her a chance.
Shadeez arrived at Gizer Battlestation, though the meeting was complicated by the arrival of the Jedi Knight Tirien Kal-Di; the Council of Reconciliation had been apprised of Arstyn's planned meeting with Shadeez and sent Tirien to Gizer to both bring Shadeez back into the fold and ensure Arstyn did not plan to leave the Republic. Out of respect for Tirien's own achievements, and on Shadeez's request, Arstyn included the Pantoran Jedi in their discussions, though he made clear he would not hesitate to make alliances with "rogue" Jedi to protect his homeworld.
Shadeez and Arstyn agreed to combine forces and to sign an accord over lunch. As they prepared a ceremonial toast with Gizer ale, however, Alecto, disguised as a servant, approached with the ale, distracted them by spilling it, and then struck both down with her lightsaber. Her blow carved open Arstyn's torso from shoulder to hip, killing him instantly.