Another Yngling king in Sweden was Ingjald Illrade. From his saga, we learn something about how kings were chosen. When a king died, his successor was supposed to attend the funeral feast and there sit at the foot of the throne.
A huge horn beaker was brought in. The heir had to pledge to do some mighty deed of valor, and then drain the beaker to the bottom. After this ceremony, he was led to the throne and proclaimed king.
When Ingjald planned the funeral of his father Anund the Cultivator, he invited all the petty king and jarls (earls) of the neighboring areas to attend the feast. There he stood up, made a vow to increase his kingdom by the half on every side, and drained the beaker. He then allowed his guests to drink until they became intoxicated. At this point, he left the hall, surrounded it with his men, set it on fire, and thus killed all his potential rivals. The people hated him for his treachery, and named him Ingjald Illrade, or ill-ruler.
King Ingjald is said to have been the last king of the Yngling dynasty to rule in Sweden. According to the sagas, he died about 600 AD, by setting fire to his palace on Lake Malaren and thus destroying both himself and his daughter. It was a fitting end for a man who had murdered his vassals by that very method.
In Swede, Ingjald Illrade was succeeded by Ivar Vidfamne (Wide Reacher). Ivar started a new dynasty, called Ivarska after himself.
The line of the ill-ruling Ingjald, however, did not die out. His son Olof Tretelgia (Olaf Tree-Hewer) escaped to Norway, where he became the progenitor of the Norwegian Yngling kings.
[Royal Families of Medieval Scandinavia, Flanders, and Kiev]