Since the times of Aenarion, it was an Elven custom for the Phoenix King to marry the Everqueen; from their union will be born a female to succeed her mother as avatar of Isha and lady of Avelorn. Such is believed to be the case for Aliathra, officially the daughter of Phoenix King Finubar and Everqueen Alarielle.
Contrary to popular knowledge amongst the High Elves and most of the Warhammer World as a whole, Aliathra, is actually an illegitimate daughter who was fathered by Prince Tyrion. Some time before the full onslaught of the End Times and upon a high level of concern from Tyrion, who wanted to go help her escape.
In the Shadow of Nagashizzar
Whilst ambassador between the High Elves and High King Thorgrim of the Dwarfs, Aliathra, the future Everqueen of Ulthuan, had been captured — the Vampire Mannfred von Carstein had ambushed her escort with a mighty army of Undead before the gates of Karaz-a-Karak. Thorgrim cared little for the fate of any Elf, but honour had demanded that he take action. Thorgrim’s throng followed Mannfred to Nagashizzar, arriving to find the High Elves had already sent their own army, a force led by the renowned Prince Tyrion. The High Elves had succeeded in rescuing Aliathra from the blasted citadel, but Mannfred had unleashed a counter-attack — an Undead host of incredible size. At Thorgrim’s gruff command, the grim warriors of Karaz-a-Karak joined the fray and, in the end, it was Dwarf steel that turned the tide. Thorgrim, his household Hammerers at his back, crushed the Necromancer cabal that gave Mannfred’s army its dread unlife. Alas, the blow fell too late.
Even as his minions perished beneath gromril hammers, Mannfred hacked his way through the Elf ranks, wounding or slaying many of their heroes and once again captured Aliathra, spiriting her away into the darkness. Thus was a great victory soured. To make matters worse, Tyrion showed no gratitude to the Dwarfs, instead blaming them for the loss of Aliathra.
Soon after the escape of Mannfred, he had the Fay Enchantress, now a Vampire herself who had tricked a group of travelers into believing she was a mere mortal woman of Bretonnia, bring his bone cage of sacrificial victims, including the exceptionally powerful Aliathra and Volkmar the Grim, to him. Despite some issues with the raw holy power given off by Aliathra instinctually when faced with the unholy, the transfer of the prisoners was a success.
Tyrion's behavior in this trying time led his brother, the Loremaster Teclis, to come to him and, by way of implications in his speech, confirm the illegitimacy of Aliathra's parentage and her lack of true claim to the throne of Everqueen due to Tyrion and Alarielle's shared passion.
The End Times
The nine victims who had been kidnapped for the unholy rituals in mind had not been whimsically selected; rather, their bloodlines had been identified by an enciphered prophecy buried in the books of Nagash. For their first use, the blood had turned Sylvania into land beyond the power of prayer. The air was thick with apostatic enchantment, an unholy miasma that sapped the courage from even the most valorous souls and dissipated the cleansing energies of the faithful.
By Mannfred's inaccurate reckoning, Aliathra, like the similarly kidnapped Fay Enchantress and Volkmar the Grim, was nothing less than a demigod, whose power lay scantily concealed beneath a thin veil of flesh. As such, she had been taken not only to destroy the gods' power to influence Sylvania, but also for the ritual to resurrect Nagash.
An Accursed Alliance (Autumn 2523 – Summer 2524)
At one point prior to the Twelfth Battle of La Maisontaal, Mannfred visited her, wanting for her to know that she was more important to him than he had previously believed, yet he also wanted to know what a supposedly enthralled captive such as herself could actually manage to hide from him. Though she managed to see some of his concern over the idea that her people would come to her rescue, he began to use his powers as a vampire to bore into her mind, sapping her will despite her best efforts. His overpowering compulsion for her to surrender and give up all hope of rescue nearly caused her capitulation, if not for Arkhan the Black coming and telling Mannfred that they had more important things to do than watch the great Mannfred von Carstein demonstrate his mastery over a shackled mortal. This sarcastic comment was enough to momentarily shift Mannfred's concentration, enough for Aliathra to muster her willpower as Mannfred angrily stalked away. In this time, she gave a brief prayer to Isha and renewed her silent song, a cry for help that was so subtle that Mannfred was unable to hear, but could be heard by rescuers abroad.
The Ritual (Autumn 2524)
Remaining bound on the edge of the stone circle for the ritual, Aliathra's defiant hope grew with the knowledge of Eltharion's arrival in an attempt to rescue her, knowing that his determination was second only to that of her father.
Upon her turn for the ritual, Aliathra was grabbed by her hair and forced head and torso over the cauldron's rim, a bone dagger held to her throat with Arkhan's other hand. He was momentarily interrupted by Eltharion's arrival, but quickly murdered him with necromancy and caused him to disintegrate into dust.
Nearing the moment of her death, Aliathra defiantly stood up once more and told the liche that her father would destroy him for her murder, showing no sign of faltering when he told her that said father had been killed already.
When brought before the cauldron used to bring about the rise of Nagash, she did not resist, instead stepping forward to Arkhan and pressing her bound hands against his chest. The resultant brief flare of white light caused Arkhan to recoil as if burnt. Upon being demanded to tell what she had done, the Everchild merely said, "You'll find out."
Due to his anger and his desire to complete the ritual, Arkhan thereafter slit her throat over the cauldron, spilling her royal blood. The blood spilled into the cauldron and mixed with that of the previously slain Fay Enchantress, and the dying Everchild was left to twitch in her death throes as the ritual moved toward completion.
Due to the fact that Aliathra was the daughter of Tyrion, and not Finubar, the ritual gave Nagash the Curse of Khaine, rather than the divine blessing of Asuryan, for a time sapping his strength and will rather than granting him the godhood he sought.