In ages past, Rebma was the beautiful underground reflection of Amber, ruled by Queen Moire, who rivalled Gendo in age, power, and wisdom. Then for reasons which remain unclear, one-hundred and forty years ago, Rebma was replaced by a mile across whirlpool some ten miles off the shore. It was surrounded for miles by shadow storms which ebbed and surge irregularly. Sometimes the gulf of Amber was completely blocked off by them, sometimes not. The Lighthouse of Cabra provided guidance for ships through the storms, enabling trade to continue, although this made Amber's trading quite a bit more dangerous and prompted the creation of the Amber Air Fleet.
At the same time as it sank, all the Water Flawed and Broken Patterns of Shadow evaporated, creating a cosmic imbalance and annhilating much of the Coral Circle trading shadows of Rebma. The Coral Forest Nedra which guarded the approaches to Rebma was torn apart by the continual shadow storms.
Prince Derith and most of the royal family of Rebma were lost in the Whirlpool, along with the Demi-Jewel of Water. But not all Rebmans were within Rebma when it sank. Many of the surviving traders blended into the surrounding nations, and a large group of expatriates lived in Atlantis for a time, eventually forming the core of those who repopulated the city after it's reconstruction. Most Rebmans blame Annadil for the disaster, and a few blame Derith, believing he must have botched some experiment. But a small group of Rebmans, founders of the extremist group 'Bloc Rebmaquois' blamed Amber. They want to see the earth open up and swallow Amber. They want to see Castle Amber fall into the sea. They are convinced that this is an effort by Amber to further oppress the Rebmans, and they're not going to take it any more. Sabotaging ships, blowing up buildings, stockpiling gunpowder that failed to explode under the Town Hall of Amber City (The so called 'Gal Fawkes' disaster), and taking random potshots at Princes of the Blood from clock towers was their typical modus operandi.
A century ago, during the Herald Crisis, Rebma resurfaced and the storms vanished. Initial investigations showed only ruins to remain. But Bloc Rebmaquois rapidly seized the city, and their leader, Dolphin, crowned herself Queen Ynell I of Rebma.
Prince Lucien appeared in Amber the same day Rebma returned, and proclaimed himself son of Derith and Moira, Crown Princess of Rebma (and eldest daughter of now deceased Queen Moire). He staked a claim to the throne, and successfully enforced it through strength of arms and the aid of a number of family members. However, the reign of King Lucien was short-lived, as Doctor Wu-Love (Wu-Anno) blew him, his army, most of the remaining Rebman royals, Greyswandir, and a fair chunk of undersea landscape to bits with a massive Primal Chaos bomb. Why he did this in Rebma instead of at the Chapel of the Serpent where his actual -enemies- were remains unclear.
Following the carnage, the Crown of rebma devolved upon Queen Yuriko of Amber, who passed on it for personal as well as political reasons. Miki, Prince of Amber, accepted it, and has ruled in Rebma for the past century. The line seems secure, with the birth of Crown Princess Kaname (and a fair degree of people who follow after her) and Miki has proven himself to be an effective ruler, supervising the reconstruction of Rebma well.
Rebma is not entirely trouble-free, as the remnants of Bloc Rebmaquois reformed themselves into 'Rebma Liberte,' a terrorist group with the stated goal of 'liberating Rebma from the tyrannical oppresion of Amber.' They mostly do what Bloc Rebmaquois did, only with far less effectiveness since they lack Dolphin, whom they cannot even spring from prison despite numerous attempts.
Tohru is not the secret leader of Rebma Liberte. Really.
Other notable Rebmans and Rebman-related people include: