Assassination of Empress Fel

The assassination was planned by several high ranking Imperials, who were resentful of the empresses willingness to work with both the Jedi and the Galactic Alliance Remnant. They worked together to cripple the protection at the Imperial Palace on Bastion, and succesfully won the support of the majority of the Imperial forces on the planet.

Prelude
"This child is no more fit to be Empress than a Twi'lek dancer is. We must show the galaxy the the Empire does not take orders from its lessers" - Volanus Xavier.

The assassination of Empress Marasiah Fel was orchestrated by Grand Admiral Volanus Xavier, senior captains Tyresius Morne, Gilan Paerus, and general Trask Artaeus. It was planned since the end of the Emergence Wars, during which the empress sent Galactic Empire forces to the planet Orvim, in order to prevent the Jorian Sovereignty from disrupting the Triumvirates exploration into the Unknown Regions.

Many in the Empire were disgruntled by Fels' willingness to work with both the remnants of the Galactic Alliance, and the Jedi Order. Xavier believed that Fel was naive, and too inexperienced to lead the Empire, which was being sent to its' doom. He believed that in order for the Empire to be brought back to its' former glory, its leader needed to be replaced.

Due to his charismatic nature, and extremely sharp tactical sense, Xavier had the support of most of the Imperial fleet, and was well liked by his fellow officers. Due to his status, he was able to convince several senior captains, admirals, and general Traks Araeus, who was in charge of the defence of Ravelin, Bastions capital.

Buildup
"We'll meet aboard the Sword of the Empire, to discuss the fate of our Empire" - Grand Admiral Volanus Xavier, to the rest of the conspirators.

The conspirators, senior captains Morne and Paerus, along with general Artaeus, met with grand admiral Volanus Xavier aboard his super star destroyer, Sword of the Empire, to discuss plans for the removal of Empress Fel. Xaviers' crew was completely loyal to him, rather than Fel.

The four conspirators met on the super star destroyer, Morne and Paerus were in charge of putting down any loyalist resistance, and blocking any transmissions  that would call loyalist forces to Bastion. General Artaeus was charged with clearing a path for the Imperials loyal to Xavier to the Imperial palace.

Meanwhile, Imperial stormtroopers and soldiers loyal to Xavier and his fellow conspirators were slowly injected into units on Bastion that were assigned to Imperial Knights currently on the planet. This was to ensure that the Knights would easily be eliminated when Xavier and his men moved in on the Empress. General Artaeus' forces, the 14th Infantry, supported by the 222nd Stormtrooper batallion landed on the planet, with the vast majority of the officers and troopers loyal to Xavier, on the pretense of shore leave.

Imperial Knight Koros Vann pointed this out to fellow knight Tael Grennem, as they watched Imperial ships deliver their troops to the marshalling zones outside of Ravelin. However, neither knight suspected treachery, as the Imperials were only following their orders, and since no one on Bastion had any reason to suspect the Stormtroopers or Xavier of treachery.

After preparations had been made, and both captain Morne and Paerus had returned to their ships, Volanus was approached by Margral Finn, who identified himself as a Dark Jedi, and claimed that he had 'acquaintances' that knew the layout of the Imperial palace. Despite not trusting Finn, or any Jedi in particular, Xavier believed that he needed every possible advantage, and so accepted Finns' offer, planning on betraying him once he'd seized power. The grand admiral was, however, unaware of Finns true identity as the Sith lord, darth Quell.

Arrival at the Imperial palace
"I didn't know the fourteenth infantry or the two hundred twenty second was stationed here"

"They aren't. Shore leave, before they head to Felucia" - Imperial Knights Koros Vann and Tael Grennem observing the arrival of the 14th Infantry Regiment and 222nd Stormtrooper division at Ravelin.

The Imperial forces loyal to Volanus Xavier jumped in system, and Xavier, along with the dark Jedi Margral Finn, and several squads of stormtroopers, used Imperial gunships to make their way to the Imperial palace, where Xavier used his authority as an Imperial Grand Admiral to gain entrance. They made their way inside and towards the Empresses throne room, escorted by several Imperial knights.

Darth Quell managed to conceal his true identity from the knights, pretending to be an aide to the grand admiral. However, the leader of the Imperial knights, Antares Draco, was suspicious of Volanus Xaviers motives, and made him and the stormtroopers with him wait outside, guarded by an Imperial knight, and several guardsmen. Darth Quell, sensing the Imperials suspicion, decided to act, Force pushing the Imperial knight into the wall, and drawing his lightsabre.

The Stormtroopers with Xavier opened fire on the guardsmen, killing most of them, and Magral Finn engaged the Imperial knight in a lightsabre duel. The Stormtroopers finished off the guardsmen in the room, although they took several casualties, when they stormed the throne room. Antares Draco, along with several other guardsmen, managed to kill both squads of Stormtroopers, although Magral Finn, having killed the first Imperial knight, arrived, along with more troopers, and several squads of Imperial soldiers. Faced with overwhelming odds, and Magral Finn, who had cut down several Imperial guardsmen on his own, Antares was forced to flee.

Assassination of the Empress
"This is treason, grand admiral"

"No, Fel. This is the Empire" - Marisiah Fel and Grand Admiral Volanus Xavier

After the last of the guardsmen had been slain, Xavier, Finn, and Imperial troops loyal to the grand admiral arrived. The empress attempted to convince the Imperials backing Xavier that they were following a traitor, but when they refused to assist her, she accused the grand admiral himself of treason. He replied by informing her that it was the Empire, not treason, and promptly shot her with his blaster pistol. Darth Quell, in his persona as Magral Finn, congratulated Xavier on seizing the title of emperor, and departed the palace, leaving the planet shortly afterwards.

Aftermath
"Now, gentlemen, we can go about the business of running an Empire properly" - Grand Admiral Volanus Xavier.

After the death of the Empress, Volanus spread rumours that Antares Draco and his Imperial knights were responsible for the death of Fel, and incited much of the Imperial populace against them. In addition, he ordered all Imperial units to turn on any Imperial knights they came across, with lethal force. This lead to the deaths of many knights, that eventually sought asylum with the Jedi, effectively ending the organization. Most of them went into hiding or were absorbed into the Jedi Order. Grand Admiral Xavier was hailed as a hero for revealing the treason of the Imperial Knights, and was soon coronated on Bastion.