Tear of the Fallen
The Tear of the Fallen is a Space Hulk whose core was formed during the Eldar Fall. At the very core of the Tear of the Fallen is a pre-fall craftworld, the space hulk it now is bears the shape of a tear or drop. Through the warp and beyond, the Tear of the Fallen contains Eldar relics within, along with whatever it has added over the millenia drifting through the warp. About 300 years ago an attempt was made by the Eldar to destroy it. Their most powerful weaponry was unable to destroy it (for that matter even scratch it due to a strange field) and the Eldar believe that perhaps some entity controls it with malicious intent.
The Tear of the Fallen has always remained floating through old Eldar space but has now been seen emerging, orbiting human worlds for a few days before warping to the orbit of another human world - almost as if searching for something.
As Khaine broke Vaul the Artificer and chained him to his anvil, Vaul cast a single blade into the warp. The blood of Khaine was drawn by this blade. According to Eldar myth, this blade was in possession of the leader of a small craftworld, called the Tear of Isha. Some say that it was the sword that cursed the craftworld but slowly their leader became reclusive and would lock himself within the depths of the craftworld emerging rarely to order a new direction as if he was searching for something else. Then, instead of mutiny his subordinates began to flee the craftworld in the time of the Fall. Joining with Exodites and leaving the ship there were few left to control the small craftworld. The commander flew into a rampage when he emerged months later slaying everyone aboard - an action which pulled his craftworld in the warp, not to be seen for a thousand years.
The Tear of the Fallen as it is called is known to Eldar for what it is. A cursed place with the core of a craftworld housing an artifact of immense power - one of the 99 blades forged by Vaul himself. The sword was used by Khaine to defeat Vaul and still bears the blood of both gods upon it. As such, for a time many Eldar begain searching within the space hulk for it but it was a twisted place within, haunted and evil. The Eldar decided that destroying it was the only option. With their most powerful weapons they fired into the space hulk - it emerged from the bright balls of flame and light completely unscathed and vanished into the warp pulling several ships with it, to become a part of the Tear of the Fallen.