Ulthwé is one of the largest and most populous Eldar craftworlds remaining since the Fall of the Eldar and it orbits the Eye of Terror.
Via our good friends at Lexicanum
Ulthwé was caught in the gravitational pull of the Eye of Terror when it formed during the birth of Slaanesh and now orbits it, perilously close to ultimate absorption and under regular attack from the denizens of the Eye of Terror. Being so near the Eye, the Craftworld has fought long and bitterly against Chaos forces. Areas within the Craftworld lie in ruins from battles fought within Ulthwé itself between Eldar and Chaos raiders. The location of Ulthwé is the reason given by Ulthwé for maintaining such a large number of Warlocks, while others believe it more due to be their location causing exaggerated psychic powers in the Ulthwé population that causes the emergence of more Warlocks.
Whatever the reason, many Warlocks and other psychic warriors follow the Ulthwé armies to battle and their skills are even more advanced than other Craftworlds, being able to see further ahead in time and with greater precision. One of the more famous and integral aspects of the Ulthwé Craftworld is that of the Seer Council. Formerly led by the now deceased Eldrad Ulthran, the council both overtly and secretly interferes with other races in an attempt to steer fate in their favor. This has no doubt allowed Ulthwé to survive so long in such a perilous position. Part of this method means that attacks carried out by the Ulthwé may seem purposeless or as serving no immediate reason.
They are instead often meant to influence events far in the future, which has given the Eldar the reputation of being capricious and random. Through its interference with other races, Ulthwé is supposedly responsible for several devastating events in the Imperium, including the Second War for Armageddon, the Sanapan Scouring, the Mortis Annihilation and the Third Coming of Orian. Because of Ulthwé’s enormous reliance on seers and warlocks, the Craftworld has found itself lacking in Aspect Warriors.
To compensate, it maintains a highly trained standing army known as the Black Guardians because of the colour of their armor, dedicated to rapidly responding to the many attacks from the Eye of Terror. Thanks to this force, Ulthwé has survived years of constant attacks. The symbol of Ulthwé is the Eye of Isha, symbolizing the sorrow of their goddess ancestor after Asuryan ordered her separated from her Eldar children. It is said that Vaul forged the tears into spirit stones, making her grief beneficial to the Eldar today. Ulthwé has since taken the tear as their symbol to remind themselves of the godhood they lost long ago.
The Ulthwé Strike Force consists of forces adept at using the Webway to mount sudden and perfectly co-ordinated attacks. Forces are comprised primarily of Storm and Guardian Defender squads, supported by vehicles crewed by Black Guardians (Support weapons, War Walkers, Vypers and Jetbikes). Famous locations include: Calmainoc – This is the name given to a great space dock that is not strictly located within the Craftworld but rather to a Warp portal that was hardwired into the structure of Ulthwé itself. The portal is indistinguishable from the main doors though the actual harbor could be located anywhere in the galaxy or even beyond it. The only certainty is the fact that the way in and out of Calmainoc is through Craftworld Ulthwé. Ghreivan’s Gate – A circular frame that is decorated with several runes that stretched across several dimensions.
This gate is actually a Warp Portal and one among hundreds that existed in the Craftworld and served as access points to Warp routes that were designed by the original architects of Ulthwe in order to allow its inhabitants access to distant locations in a matter of moments.