Isholy was where Shuri hid Yuta for a long time, after he was separated from his siblings in order to hide the Power of the Name. Yuta somehow managed to travel from Isholy to Willarv between the time of the Cataclysm, when he was inexplicably stranded in the human realm, and his first meeting with Leez Haias and Asha Rahiro in N15.
Eiraheeari Catroshife (Ari) is an orphan from Isholy, according to his profile on Currygom's blog. His parents had visited Willarv, with Ari in tow, on business shortly before they died in the Cataclysm.
In a flashback, young Brilith had posters of three planets, including Isholy, on her wall.