Onaya was a non-corporeal lifeform with telepathic and psionic abilities. As of 2372 it was at least two thousand years old. It fed on the neural energy of gifted individuals, including the Roman poet Catullus, the British poet John Keats, the author Revalus, the Cardassian architect Tavor Kell and the writer Phineas Tarbolde of Canopus Planet. Onaya was also familiar with Vulcan and Native American culture.
Onaya, who took the corporeal form of a female humanoid, was also a "muse" to the individual she associated with, allowing them to free creativity from their mind that they might be unable to tap into normally. A side effect of this was that Onaya's draining of an individual's neural energy eventually killed them.
Onaya came to Deep Space 9 in 2372, where she encountered Jake Sisko. She helped Jake to write Anslem, while draining his neural energy. This led to the dilation of the capillaries in his cerebral cortex, which caused Jake to collapse in the Replimat. Onaya later came to him in the Infirmary and took him to a junction in the station's access tunnels near the reactor core. Onaya drained Jake to the point of death, but he kept writing his novel. Captain Benjamin Sisko later found them and confronted Onaya.
The entity told him that what it gave the people it "touched" was a type of immortality. They and the works they created with her as their muse would be remembered for generations. As Sisko raised his phaser, Onaya transformed into her non-corporeal state and left the station.
Sometime later, Jake expressed regret that he could not take credit for writing Anslem due to Onaya's influence, but his father told him she may have brought out the words for him, but his creativity was real and within his reach. (DS9 episode: "The Muse")
Despite his father's words, Jake found it difficult to perceive Anslem as his own work, as he felt it was "tainted" by Onaya's influence. He shook this thought off eventually and had published it by the 25th century. (DS9 - Prophecy and Change short story: "Revisited")