In the ongoing Reydovan Empire storyline, Shadowgarde Castle was the citadel of Artimus Devaneaux. The name of the castle was created by the real-life Joshua Underwood in 2005 with a WarCraft-sounding name (along the lines of Stromgarde, Tiragarde, etc.), and it was used originally as the focus of a ongoing Imperium-Chaos campaign in Warhammer 40,000 between himself and his stepfather. For the image seen here, Underwood used an image of Kilkenny Castle in Ireland, reduced the brightness significantly to give it that dark, evil feeling, and used Greg Martin's "In the Shadow of the Stars" as a terrain backdrop.
Located near the Tuolumne Mountains on Reydovan Prime's southwestern continent, the city of New Valley Forge was once a center of commerce in the early reign of Emperor Kiran Joshmaul I. Named for the place where General George Washington and his men made winter quarters in the winter of 1777-1778, New Valley Forge was ruled by the Devaneaux family, led by the corrupt Lucian Devaneaux. Lucian's son Artimus proved to be even worse, as he was responsible for killing his mother in 2347. Artimus led a reign of terror that lasted throughout his military career. When he was a general in the Imperial Marine Corps, Artimus ordered the construction of Shadowgarde to serve as his personal fortress after the abandonment of Castle Devaneaux. Some years later he assassinated Lucius Tyrael, the Minister of State, for some minor squabble. As Imperial troops tried to arrest him, Artimus unleashed a powerful psionic storm to wipe out New Valley Forge, and it remains in ruins today.
Upon his arrival in Montagne Noire, Artimus was tried, convicted and sentenced to death in January 2375, and executed two months later. But through some kind of medical science or evil psionic power, Artimus rose from the shallow grave in the city he had burned to the ground. Regenerating his rotted flesh over time, Artimus eventually toppled the Reydovan government, led by Chancellor Joshua Underwood, and began a reign of terror and genocide that would have repercussions in their neighbor states, including the Federation and the Klingons. He returned to Shadowgarde, which became Artimus' operational headquarters and pleasure house.
In addition to nearby Crow's Point Penitentiary, the dungeons beneath Shadowgarde Keep are a living nightmare for those imprisoned in it. With his alliance with Dr. Robert James Broussard, a lunatic biogeneticist, Artimus has plans to unleash some kind of plague against telepaths. In addition to potentially crippling the Federation by destroying the telepathic/empathic people of Betazed - which Broussard has sworn vengeance against - Artimus hopes to develop a "superstrain" to kill his nemesis Kiran Joshmaul. The labs in Shadowgarde are at full production to develop other kinds of vile weapons, some too terrible to contemplate.
On December 13, 2375, Captain Jasmine Blade - a Starfleet Special Forces officer sent by Joshmaul to infiltrate Artimus' regime - confronted the Mad Emperor in the throne room of Shadowgarde. Outside the fortress, Starfleet Marines and militiamen from the province of Easthaven, under the command of General David Highland, attacked the citadel's exterior generator (that powered the castle's security systems) and completely destroyed it. Realizing defeat was imminent, Artimus activated explosives buried underneath the fortress and made his escape.
As the Starfleet and Reydovan troops made their way quickly back to Easthaven, the powerful weapons underneath Shadowgarde exploded, incinerating the ruins of New Valley Forge and sending a shockwave that destroyed every small town in an eight hundred mile radius; even the suburbs of Montagne Noire itself were affected.