The only truly benevolent member of the Aeldari Pantheon, it is said that it was Isha who intervened and created all non-Aeldari life in the universe once Asuryan, the ruler of the Aeldari Pantheon, no longer took interest in his creations and their solitude.
It was also Isha who pleaded on behalf of the mortals when the Aeldari God of War, Kaela Mensha Khaine, attempted to slaughter the Aeldari, having heard from the Crone Goddess Morai-Heg that the Aeldari would one day cause his downfall, and it was Isha who secretly continued to guide the Aeldari when Asuryan interdicted any direct contact between mortals and Gods by separating the Immaterium from the Materium.
After the Fall of the Aeldari, Isha was about to be devoured by Slaanesh like all of her divine brethren, but she was rescued by the forces of the Plague God Nurgle. Today, many Aeldari believe that Nurgle keeps Isha in a cage in his Plague Gardens in the Realm of Chaos, where he tests out every new disease and pestilence he creates to affect the mortal realm. But Isha still seeks to aid mortals by whispering the cures for each of Nurgle's plagues into the universe to be discovered when they are most needed.
War in Heaven
It was Isha who had inspired the creation of Asuryan's barrier between mortals and their gods, as she had wept over the destruction that Khaine, as the God of War and Murder, was causing amongst her children. It is also said that the first Spirit Stones were crafted from her tears so that the gods and mortals would be able to communicate with each other once more through the barrier erected between the Immaterium and the Materium.
One of these stones was given to Isha and the rest were handed over to the Aeldari so that their prayers might be heard. When Asuryan learned that his directive that the Gods were to have no further contact with mortals had been violated, he gave Isha and her husband, Kurnous, to Khaine to do with as he wished.
Khaine tortured the two of them in a burning pit until Vaul, the Aeldari God of Crafting who was Isha and Kurnous' uncle and was moved by their plight, struck a bargain with the War God to craft 100 enchanted swords, the Blades of Vaul, for him in one's year's time. In exchange, Khaine promised to release his fellow Gods from their prison in his realm.
The Smith God worked long and hard at this task and managed to forge all of the blades by the deadline except for the last one, which lay unfinished on his anvil. In order to trick Khaine, Vaul substituted the last blade with a mortal one which he delivered to the war god, who released his two captives. The three gods quickly departed.
But Khaine was quick to discover the subterfuge and cried out in rage. He called the smith god a cheat and vowed revenge. He immediately set off to track Vaul down and make him pay. The conflict that followed, known as the War in Heaven, polarised the gods, as Khaine's faction and Vaul's faction engaged in bloody warfare for an eternity.
Gods changed sides, great deeds of heroism and of terrible evil were performed by both factions, and the war was mirrored in an internecine struggle between the Aeldari in the mortal realm. Asuryan himself never took a side, watching the carnage impassively, slowly coming to regret his impetuosity in sentencing Isha and Kurnous to Khaine's tender mercies.
Vaul reforged the final sword, the one that he had failed to finish for Khaine, the greatest of all, and called it Anaris. Armed with this weapon, Vaul strode forth to do battle with Khaine. It was a long, hard-fought struggle, but even with Anaris, Vaul was no match for the War God. Khaine cast down Vaul, maiming the smith, and bound Vaul to his own anvil.
However, the falcon, Faolchú, consort of the Great Hawk who had fought for Vaul, took the sword Anaris and delivered it to Eldanesh, the greatest warrior and leader of the mortal Aeldari. With Anaris in hand, Eldanesh of the Red Moon took up the fight and faced Khaine in single combat. Eldanesh fought well, but in the end, he too was defeated by Khaine, his body crushed by the God of War.
As Khaine slew Eldanesh, his hands began to drip with red blood. Forever after he was to become known as Khaela Mensha Khaine, which means "Khaine the Bloody-Handed" in the Aeldari Lexicon. By this time, Asuryan, the greatest of the Aeldari Gods, had seen enough of the slaughter and proclaimed the War in Heaven over. Khaine had gained his vengeance and left the field satisfied.
Capture by Nurgle
Many millennia later, like Cegorach who fled into the Labyrinthine Dimension of the Webway, Isha was not destroyed outright and absorbed by Slaanesh like the rest of the Aeldari Pantheon after its birth during the Fall of the Aeldari. Slaanesh vanquished her as it had all of the other Aeldari gods within the Warp, but only took her prisoner rather than absorbing her energies outright.
What fell purpose Slaanesh had in keeping Isha alive, none amongst the Aeldari now know, but the Prince of Pleasure was ultimately denied its spoils: for some reason, Nurgle, the Plague Lord, waged war against Slaanesh to "rescue" the Aeldari goddess. Why Grandfather Nurgle intervened is unclear, although some Aeldari savants believe that one of the oldest of the major Chaos Gods wanted to give the youngest amongst them a good lesson about his proper place in the order of things.
What is known is that Nurgle's daemonic forces proved victorious and he took the Aeldari goddess back to his domain in the Realm of Chaos. A goddess of rejuvenation and a god of decay seemed an odd pairing, but Nurgle came to adore his new companion like no other being in the universe.
However, he shows his love in the only way a Chaos God knows how. Nurgle keeps Isha imprisoned in a rusted cage within his personal manse in the corner of his Plague Gardens. It is there that he keeps the cauldron where he mixes the elements that create all of his plagues and pestilences. Nurgle tests all of his new, virulent creations upon the body of his "companion."
As the Goddess of Healing and the spiritual embodiment of health and growth, Isha can cure herself of these afflictions, but the Plague Lord gains an idea of their potency by watching how much power the Aeldari goddess must expend to cure herself. If he is pleased with how hard Isha must struggle to conquer the disease, Nurgle releases the new creation upon some unsuspecting world, but if not, he starts over, working at his cauldron until he has something new to give to his companion.
Isha accepts her lot stoically and fights back against the Plague God's evil in the same way she once fought against Khaine, whispering the cures to these new diseases into the universe so that mortals might know them and resist the hideous designs of Grandfather Nurgle.
- Codex: Chaos Daemons (6th Edition), pg. 15
- Codex: Chaos Daemons (4th Edition), pg. 82
- Warhammer 40,000: Compilation (1st Edition), pg. 36