Lacuna is a moon of Drakonius, the lesser of two which includes itself and the closer, larger moon Ezuno -- although, Ezuno and Lacuna are speculated to be about the same size in some scientific circles, and that Lacuna's distance from the planet makes it appear smaller than Ezuno. This was only recently brought up with the advent of astronomy and telescopes in Thunder's Shore. Whatever, the case, Lacuna's orbital period is about 49 days, meaning it will return to its former phase within about a month and a half, as opposed to its larger partner Ezuno, which takes roughly 27 days to orbit. Lacuna's many faces are visible, but Ezuno's are not; it is tidally locked to Drakonius.
Lacuna in religion and culture has been typically seen as a child or wife of Ezuno; they are said to be of a divine union that was sent to watch over the planet in its infancy, and have not yet left.