Many monarchs have come and gone
One drowned in poison, another succumbed to flame,
Still another slumbers in a realm of ice. - Aldia, Scholar of the First Sin
We do not know the origins of the Sunken King. In his travels he came upon a slumbering dragon. He erected the Eternal Sanctum to protect this dragon in its slumber. Perhaps he realized that if the dragon were ever to awaken it would destroy his kingdom, but more likely he regarded it with awe. Priestesses were ordained to sing to the dragon, a lullaby that would preserve its deep slumber.
The Sunken King entertained troubadours and travelers in his courts. A child of the Dark called Elana came to him and she became his queen. It may be that afterwards, Elana established the order of priestesses, claiming that they were a necessity in order to preserve the dragon's sleep. The Sunken King considered sorcery and hexes taboo in Shulva. However, their miracles were highly advanced and there is evidence that (see Sanctum Shield) sorcery may have become more popular later on in the King's reign. The King also cultivated various balms and plant life that would provide benefits to those adept at miracles as well as strength and dexterity based tasks
The Sunken King spared no expense in defending the dragon from invaders. His Eternal Sanctum was considered a bulwark, and dominated the landscape of the city. It was filled with traps, hidden switches, and narrow passages which would encumber any large invading groups. The entry to the inner section of the Eternal Sanctum was secured by a large stone key that had to be inserted into a specific annex in order to gain access. The Sunken King also created an order of knights known as the Sanctum Knights, who were devoted to defending the slumbering Sinh. When Sir Yorgh invaded Shulva and reached the Eternal Sanctum, these Knights agreed to renounce their own flesh in a clandestine ritual that turned them into eternal stewards, essentially causing them to become only semi-corporeal.
Despite these measures, Sir Yorgh and his Drakeblood Knights invaded the Sunken King's kingdom and fought their way to the dragon. The Sunken King was killed by Sir Yorgh during the assault, whether directly by his blade, or as is implied by Aldia, indirectly by piercing the side of Sinh, the Slumbering Dragon. Today, no one remembers his name.