After the other Eliksni Houses left their homeworld in pursuit of The Great Machine (Traveler). They left one behind for the House of Rain, in case they decided to follow and rejoin with them. After years of neglect the Ketch fell into disrepair, slowly falling apart while the House of Rain struggled to survive.
However, eventually a group of Vandals, the Engineers (Not unlike Selyk's own group, The Silent Sorrows), re-discovered it and began to rebuild it. They spent years venturing out and collecting tools and materials to patch up the Ketch, eventully repairing it to the point of atmospheric flight, although without a Pilot Servitor it was unable to be flown off-world.
It was named Oath of Unity to remind the Eliksni survivors of their goal. Unite the Eliksni Houses once more.