Rebma started out life as the undersea reflection of the Pattern of Amber. The first ruler of Rebma was Queen Moins, a daughter of Cymnea (Oberon's first Queen in Amber).
When Oberon died fixing the Pattern of Amber from the damage done to it at the start of the Patternfall war, the reflection of that death also brought the end of Moins. The throne passed to her eldest surviving daughter Llewella, assisted by the two Sister Princesses, Deirdre and Cymnetta, each of which share one parent in common with their queen.
Little is known of the culture and lifestyle of the undersea Realm. What is known, is that relations would be described as strained at best between Rebma and her nearest neighbour Amber. Though Random of Amber and Llewella of Rebma both share a father, there would seem to be little love lost between them - not perhaps helped by the fact that Random was a once regular visitor to Rebma, who invariably left trouble in his wake - his first visit resulting in the then Crown Princess dying in childbirth bearing Random a son called Martin, and his next visit being the one where he carried off a royal princess (Vialle, daughter of the missing Princess Moire) to become his bride.