Isha is the Eldar Goddess of the Harvest, Fertility, Life, Healing and Growth and the mother of the Eldar race in Eldar Mythology.
In Eldar mythology Isha is the mate of the god Kurnous, the God of the Hunt. During the First War In Heaven, between the Old Ones and the C'tan and their Necron, Isha was one of the warp-derived beings created by the young Eldar at the encouragement of their creators to be used as weapons in the war. After the war ended, these war-beings formed from the collective psychic might of the nascent race became sentient and true gods of the Immaterium.
She was the only truly benevolent member of the Eldar Pantheon, and was said to intervene on behalf of mortals and was responsible in creating all non-Eldar life in the universe. After Asuryan, the ruler of the Eldar Pantheon, lost interest in the material universe, it was Isha who pleaded on behalf of the mortals when the Eldar God of War, Kaela Mensha Khaine, attempted to slaughter the Eldar and would secretly continued to guide the Eldar even when Asuryan created a barrier separating the Immaterium from and the Materium.
When it was discovered by Asuryan that Isha and her mate were communicating with mortals, he punished them giving them to his brother Kaela Mensha Khaine to do as he pleased. Isha and Kurnous were tortured by the war god, and only Vaul, their uncle, interceded on their behalf giving Khaine 100 blades. However the couple were freed, but Khaine discovered that one of the blades was of poor quality, leading him to call Vaul a cheat. The incident polarized the gods, leading to the Second War In Heaven. The war left the gods weak from conflict and were easily defeated after the birth of Slaanesh.
After the Fall of the Eldar, Isha was one of the few Eldar gods that survived being devoured by Slaanesh. Rather than being eaten and imprisoned in She Who Thirst's stomach she was rescued by the forces of the Plague God Nurgle. Since then Nurgle keeps Isha in a cage in his Plague Gardens in the Realm of Chaos, using her as a lab rat to test out every new disease and pestilence he concocts. When Nurgle's back is turned Isha whispers the cures for these ailments to the mortals.