Arissa was the alias of an Idanian undercover agent.
In 2373, Arissa came to Deep Space 9 to meet with a contact and provide him with information about the Orion Syndicate. Arissa's contact was killed by Orion Syndicate members, who later attempted to kill Arissa herself. Odo assisted Arissa in her investigation, with the two becoming briefly romantically involved. (DS9 episode: "A Simple Investigation")