The O-Mor were a sentient alien civilization native to the planet Sachem II, a homeworld located somewhere in the galaxy's Alpha or Beta Quadrants. The O-Mor were the subject of a covert Starfleet cultural observation mission prior to the Dominion War. During that conflict, however, the planet was taken and occupied by Jem'Hadar troops. Following the war, late in the year 2376, a team from the Federation starship USS da Vinci visited Sachem II to evaluate the level of cultural contamination left on the O-Mor people. The team determined that there was no harm done, owing to the O-Mor's easy-going nature.