From: Star Trek: The Next Generation
Planet: Daled IV. A race of allasomorphs - shape-shifters with the power of cellular metamorphosis to take on any form desired - who evolved two long-warring camps, one each from the always-day and always-night hemispheres of Daled IV. Their natural state is a vaguely humanoid outline of pure light, but they retain emotions. Despite their advance evolution, the two camps did not end hostilities until a peace wedding between the two in 2365.