He lived on Merriman Island, in the middle of Wallaga Lake, while his people lived on the shores of the lake. Umbarra was believed to have clairvoyant abilities, and communicated with a black duck, his moojingarl, which forewarned him of forthcoming dangers.
Many legends now exist about Umbarra and his moojingarl. One day it told him of a group of warriors coming from the far south to do battle. King Merriman remained on the island while the other men took the women and children to a place of safety and then hid in the reeds. The first to sight the approaching warriors, the King warned his men who fought a fierce battle but lost. The opposing tribesmen then set out for the island.
King Merriman threw powerful spears, and a boomerang which severed the arms and heads of his opponents before returning to him, but it was not enough. He then turned himself into a whirlwind and flew off. He passed over the fierce Kiola tribe and their wise men correctly divined his presence and that it meant the defeat of the Wallaga people and the advance of another tribe. King Merriman journeyed on to the Shoalhaven tribe to warn them but the Kiola tribe defeated the invaders and the King, whose power was finished, stayed for a time at the Shoalhaven then travelled away.
General access to Merriman Island is forbidden due to its great significance for Indigenous people – it was the first place to be gazetted as an Aboriginal site. A focus of tribal culture, the island is associated with the story of King Merriman, widely known among the Yuin Aborigines of the south coast.
Today, the Yuin operate the Umbarra Cultural Centre near the Lake. The former Wallaga Lake National Park is incorporated into Gulaga National Park.