The Dorahl Bioship is a two thousand year old vessel encountered by the Orville.
Originally captained by Jahavus Dorahl, in the middle of an expedition through deep space it was unable to finish it's voyage. Due to the self contained ecosystem that was capable of renewing it's own resources the ship could survive long enough for help to arrive. Unfortunately, they aren't found for thousands of years and the residents onboard develop their own culture. Believing the ship to be the entire known world and Dorahl to have been a godly figure in need to absolute worship.