I-Chaya was a domesticated male sehlat who had belonged to Sarek of Vulcan, and then later to his son, Spock. I-Chaya followed Spock out onto Vulcan's Forge when the young boy decided to embark on his kahs-wan challenge early, and defended him when Spock was attacked by a wild le-matya. Though I-Chaya managed to drive the attacker away (with the help of a man calling himself Selek), he was severely wounded and poisoned by le-matya venom. Young Spock, putting logic above emotion, asked that the Healer tending to the sehlat put an end to his suffering. I-Chaya's remains were returned to Sarek's family estate and given an honorable burial. (TAS episode: "Yesteryear")
Amanda Grayson wrote about Spock’s disappearance in her journal entry for December 7, 2237, noting that I-Chaya had gone with him. She was panicked, annoyed that Sarek was working and seemed unconcerned, but reassured that at least the fat sehlat would keep her son warm in the cold desert night. (TOS novel: Sarek)
Amanda added a memorial for I-Chaya at the family's ancestral burial grounds. When Sarek and Spock visited the grounds in 2268, Sarek said he knew that the memorial had been Spock's idea. (TOS - Year Four comic: "The Enterprise Experiment, Part 5")
In 2286, while reconditioning his mind on Vulcan after fal-tor-pan, Spock wandered into the mountains and encountered a sehlat which he initially thought was I-Chaya. After controlling his emotions and remembering I-Chaya had died when he was seven, he and the sehlat repelled an attack of five le-matyas. (TOS comic: "The Needs of the One")
Leonard McCoy knew what I-Chaya’s fur felt like in the Vulcan sun, and the feeling of I-Chaya’s tongue tickling his thumb, memories left over from Spock’s katra. (TOS - Strange New Worlds VII short story: "All Fall Down")
In 2293, while meditating in his apartment in San Francisco following the death of James T. Kirk, Spock focused on the scene of I-Chaya saving his life in an attempt to center his mind. (TOS - Crucible novel: The Fire and the Rose)
- TOS episode: "Journey to Babel"
- TOS audiobook: Passage to Moauv
- TOS - Year Four comic: "The Enterprise Experiment, Part 5"
- TOS novel: Vulcan's Glory
- TOS novel: Demons
- TOS novel: Sarek
- TOS novel: Vulcan's Forge
- TOS novel: Assignment: Eternity
- TOS - Strange New Worlds VII short story: "All Fall Down"
- TOS - Crucible novel: Provenance of Shadows
- TOS - Crucible novel: The Fire and the Rose
- TOS comic: "The Needs of the One"
- TNG novelization: Unification