Born in 6442, he was the youngest son of King Jaron. He had 2 older brothers and a sister. He took the throne in 6498 at the age of 56 as his young age guaranteed more time in the throne for him. His siblings understood the logic of their father of giving him the throne, and worked well with their younger brother, as no other family had done previously. Years later this would be a forceful argument for council ruling.
In 6510 the expeditions led by Rock Biter and The Burrower uncovered a new cavern and there were calls to expand the D'ni City. Rikooth instead suggested to his older brother, who was Guild Master of the Guild of Surveyors, to study the cavern extensively, before Rikooth could take a decision.
In 6556 Rikooth married to Hisha a strong believer in Gish and the fallacy of the Great King. Though she had some influence on Rikooth, he continued in the tradition of his fathers never publicly stating his views. However, she had much more influence on their 3 sons including the youngest Kerath.
In 6601 Rikooth received extremely detailed reports (structural analysis, water supply, rock type, etc.) about the newly discovered cavern and it would be very expensive to build in. After conferring with his advisers, the King decided that Stone Tooth, and the new Rock Biter, should begin digging out more of the city proper (into the cave wall) for expansion while Burrower and Stone Eater would continue to tunnel past the cavern.
Though there had been no major incidents about outsiders for centuries, in 6676 Rikooth met with leaders to discuss their involvement. Though Rikooth understood the reasons for wishing to close down interaction with outsiders, their contribution to D'ni culture, art, construction, technology, and resources, was immeasurable; there was no way, he argued, that he would ever force strict resolutions regarding the outsiders.
By the end of Rikooth's reign the city was larger than ever, the classes were more divided than ever, and the religious beliefs divided; there was no clear majority of people who believed any one thing.
Rikooth had chosen one of his older sons as his successors. Rikooth passed away in 6731 at the age of 289; however legends told, Rikooth was on his own death bed staring out toward the King's Arch and he saw Kerath sailing through it in a boat in the shape of a massive lizard standing proudly on its prow, coming home to announce the death of his mother. As he sailed through the Arch, Rikooth apparently felt the hand of Yahvo, directing him to make Kerath the next King of D'ni.