The Farseers of Ulthwé had forseen that a large Tyranid swarm was heading on a path that would have led it to their Craftworld. Thus, in order to combat this threat, they made plans to divert the Hive Fleet's attention by striking the worlds within sub-sector Aurelia. Idranel and her forces were responsible for the seeding as well as the rise of Orkish hordes within those Imperial worlds in the sector. As the area was watched over by the Blood Ravens Chapter, Idranel and her forces came into conflict with the Adeptus Astartes.
Powerful psychic shields hid her involvement until she was sighted on Meridian where she was protected by her contingent of Warlock guards. Ultimately, she was beaten off and though she sustained some wounds, she did manage to escape from a battle with the Blood Raven Aramus. Later, she broke through the gates of Angel Forge in an attempt to overload a generator there with the intention of destroying the planet in order to stop the approaching Tyranid hordes. Idranel was ultimately slain by Sergeant Tarkus after his acquisition of the Terminator Armour from Governor Vandis's storehouse which contained stolen relics from the Blood Raven Chapter. With her death, it was believed that the Eldar activity on the planet would cease.