Enter Loki, stage left.
Andvari lived under a waterfall and would frequently change himself into a fish to go for a swim. Unfortunately for Andvari, Loki caught him in a net. In exchange for his freedom, the dwarf was forced to hand over his stash of gold and Andvarinaut. But Andvari had his revenge by cursing the ring. Heigh ho, Loki.
The trickster god was many things, but he certainly wasn’t stupid.
Smooth move for Loki, but bad deal for the dwarf king.
Hreidmarr’s other two sons, Fafnir and Regin, killed their own father to get their hands on the ring and then they turned on each other. The ring ended up conferring disaster on anyone who possessed it, just as Andvari intended.
Where is Frodo when you need him?
~ S.G. Rogers