Deral was an inhabitant of Meridian, a planet that phased in and out of a corporeal state and a non-corporeal state every sixty years. He was the descendant of an expedition to the planet which became stranded a millennia ago. His wife died, leaving him a widower.
During its corporeal phase in 2371, he met with the crew of the starship USS Defiant and worked with them to try and stabilize the planet. He fell in love with Jadzia Dax and considered leaving the planet to be with her, but his people needed him. Dax decided to return to Meridian and live in a non corporeal state to be with him.
However, because of her presence, the planet could not shift properly and began tearing itself apart. Dax left the planet and promised Deral she would wait for him when he reappeared. (DS9: "Meridian")