In this task, you're given a passage, further information available on a particular linked term from the statement, and a question. Your job is to generate the answer to the question by using the information provided. If there is no clear answer obtainable, output 'none'.

Passage: Dal Riata is said to have been founded by the legendary king Fergus Mor (Fergus the Great) in the 5th century. The kingdom reached its height under Aedan mac Gabrain (). During his reign Dal Riata's power and influence grew; it carried out naval expeditions to Orkney and the Isle of Man, and assaults on the Brittonic kingdom of Strathclyde and Anglian kingdom of Bernicia. However, King thelfrith of Bernicia checked its growth at the Battle of Degsastan in 603. Serious defeats in Ireland and Scotland during the reign of Domnall Brecc (died 642) ended Dal Riata's "golden age", and the kingdom became a client of Northumbria for a time. In the 730s the Pictish king Oengus I led campaigns against Dal Riata and brought it under Pictish overlordship by 741. There is disagreement over the fate of the kingdom from the late 8th century onwards. Some scholars have seen no revival of Dal Riatan power after the long period of foreign domination ( to ), while others have seen a revival under Aed Find (736778). Some even claim that the Dal Riata usurped the kingship of Fortriu. From 795 onward there were sporadic Viking raids in Dal Riata. In the following century, there may have been a merger of the Dal Riatan and Pictish crowns. Some sources say Cinaed mac Ailpin (Kenneth MacAlpin) was king of Dal Riata before becoming king of the Picts in 843, following a disastrous defeat of the Picts by Vikings. The kingdom's independence ended sometime after, as it merged with Pictland to form the Kingdom of Alba.
Link Information: none Question: How many years did the legendary king that created the Dal Riata rule for?
Answer: none