ARIES was a hyper-intelligent droid created on Iokath by the species that lived there. His original purpose was to oversee and coordinate advanced warfare simulations. Eventually, a civil war broke on Iokath, and the superweapons known as the Old Gods wiped out all organic life on the planet. ARIES remained the only self-aware droid on Iokath and over centuries consolidated power as its sole caretaker, using the massive population of service droids as his slaves and soldiers. For roughly three thousand years, Iokath remained isolated from the rest of the galaxy, hidden by absorbing almost all light from its star. The few visitors who managed to stumble upon the massive artificial sphere were tested by ARIES in brutal simulations to determine whether they were worthy of inheriting the world and its vast resources, though none have survived.
One of ARIES' many holographic disguises
In 3630 BBY a large amount of new arrivals came to Iokath when SCORPIO, herself an Iokath creation with her memories of it removed, managed to unlock the origin of herself, the Gravestone and the Eternal Fleet and brought all of those vessels to Iokath. The Eternal Fleet was crewed by a large number of GEMINI droids and Eternal Empire personnel, while the Gravestone brought the key figures of the Alliance that opposed Zakuul and Eternal Empress Vaylin. As the vessels approached and entered Iokath, ARIES activated a superweapon that emitted a bright light and knocked all organics aboard the ships unconscious, arranging and placing them across Iokath surface to test in various combat scenarios. ARIES himself, whose conciousness was spread across Iokath network at this point, appeared as a Human hologram at various technoliths, answering basic questions about history and geography.
ARIES poses as Thexan to talk to Vaylin.
Of all the numerous arrivals, ARIES took special interest in SCORPIO and Vaylin, who unlike the others were put in isolated chambers. ARIES appeared to Vaylin as a hologram of her long-dead brother Thexan, complimenting her stength and subtly probing her for information, though Vaylin soon realized the deception and found a way to escape her confinement. Eventually deciding that none of the new arrivals were worthy of inheriting Iokath, ARIES attempted to blast SCORPIO, only to discover that she used the same trick as he did, replacing herself with a holographic projection and escaping while ARIES was preoccupied. As Vaylin rallied her remaining forces and began regaining control of the Eternal Fleet warships while the Alliance forces also gathered together and found a way out of his trap, ARIES decided to bring the combat simulation to an end. He activated the massive energy shield that would destroy any vessel attempting to leave Iokath and started recharging the energy weapon, intending to kill all organics and GEMINI droids with it this time. However, his multiple holo-transmissions allowed SCORPIO to pinpoint his location at the ARIES base in Iokath's southern hemisphere and transmit it to the Alliance forces. The Alliance Commander and Vette stormed his base, eventually confronting ARIES, who lamented the damage done to Iokath in a single day. The Commander and Vette attacked ARIES, even while the Eternal Fleet laid fire to his base and the superweapon capacitors threatened to overload. Eventually, after ARIES faked defeat and attempted to backstab the Alliance Commander, he himself was shot in the back by SCORPIO and destroyed permanently. Following his death, the superweapon exploded and covered Iokath in deadly radiation, though the Gravestone and the majority of Eternal Fleet vessels managed to escape to hyperspace with everyone aboard.
In Star Wars: The Old Republic: Knights of the Eternal Throne ARIES is voiced by Kevin Michael Richardson.