The golden tree is a tree east of Rellekka south of the entrance to Keldagrim. It is a tree with unique golden fruits with sheep with gold wool underneath it. It is closed off to entry and is supposedly owned by the troll Lalli.
In The Fremennik Trials quest, you must get a golden fleece from the sheep beneath the tree to make the lyre. You need to exchange with Lalli some rock soup for one. After completing the quest, more golden fleece can be bought from Lalli for 1,000. Apart from this, the tree has no real use.