The Dilgar are an extinct race of humanoid aliens in the fictional Babylon 5 universe.
Dilgar War
The Dilgar were an aggressive and warlike species that invaded the League of Non-Aligned Worlds in 2230, three decades before the series begins. Dilgar tactics in this war were ruthless, including the destruction of entire worlds and the use of conquered races as lab animals in biological experiments. The League races were overwhelmed by the Dilgar assault and suffered heavy losses. A Dilgar victory seemed inevitable until help for the League appeared from an unexpected ally.
When the war began, the Earth Alliance had only recently emerged as an interstellar power, having acquired jumpgate technology from the Centauri. In 2231, Earth intervened on the side of the League, motivated at first by a desire to establish a reputation for the Earth Alliance as a major player in galactic affairs, and later by moral outrage as the horror of the Dilgar atrocities became clear. Earth's entry turned the tide of the war, and the Dilgar were defeated and driven back to their home system. After the war ended, the Dilgar sun went supernova, wiping out the entire species—or so it was believed at the time.
Deathwalker
Unknown to Earth and the League, a single Dilgar survived both the war and the supernova: Warmaster Jha'dur, the most infamous leader of the invasion. Jha'dur was a specialist in biochemical, biogenetic, and cyber-organic weaponry, and was responsible for many of the atrocities committed by the Dilgar during the war, having personally conducted some of the horrific experiments. These activities earned her the nickname "Deathwalker". After the war, Jha'dur was sheltered by the Wind Swords, a militant clan of Minbari warriors, in exchange for her services as a weapons expert.
The Wind Swords concealed Jha'dur's existence from the other races until 2258, when (in the episode "Deathwalker") she left Minbar and traveled to Babylon 5 with one of the fruits of her research: an experimental drug that retarded the aging process in humanoids, conferring immortality on whoever used it. Jha'dur intended to offer the drug to the Earth Alliance, but she was recognized the moment she arrived on the station. A diplomatic crisis ensued, with the League governments demanding that she be tried for her crimes while Earth sought to obtain the drug and Jha'dur's assistance in developing it.
In the end, a compromise was reached; Jha'dur would go to Earth and work with scientists to develop the drug for distribution to all races, after which she would be handed over to the League for trial. Privately, Jha'dur revealed to Jeffrey Sinclair her true reason for giving the drug to the other races: revenge. A key ingredient in the drug could not be synthesized; it had to be extracted from living beings. "For one to live forever, another one must die. You will fall upon one another like wolves. It'll make what we did pale by comparison. . . . You will become us." The resulting genocidal wars would be her vengeance on Earth and the League for the extinction of her people.
As Jha'dur's ship prepared to embark for Earth, a Vorlon warship arrived and destroyed it, vaporizing Jha'dur and the only existing sample of the drug. When asked why, Ambassador Kosh replied, "You are not ready for immortality." With the death of Jha'dur, the last trace of the Dilgar was erased from the galaxy.
Earth-Minbari War
In many ways, the Earth-Minbari War was the Dilgar's revenge on the Earth Alliance. Earth's swift and easy victory over the Dilgar caused many EarthForce officers to become overconfident, believing that other alien races would be no more formidable. This arrogance proved disastrous when humanity's first contact with the Minbari took place. The result was a bloody war that lasted two years, killed a quarter of a million humans, and nearly ended in the extermination of the human race.
The carnage was greatly exacerbated by Jha'dur's efforts as a weapons expert during her time on Minbar. When the war began, the Wind Swords approached the Grey Council and offered them devastating weapons that Jha'dur had developed in the preceding two decades. These weapons were used against the humans, a fact that undoubtedly gave Jha'dur great satisfaction.
