Which dwarf owned a magical ring that brought a curse?

The dwarf who owned the magical ring that brought a curse was Andvari.

Andvari is a dwarf in Norse mythology who possesses the ring Andvaranaut along with a hoard of gold. In the Völsunga saga tradition, Loki captures Andvari—who can take the form of a pike—and forces him to surrender his treasure. Andvari then curses the gold and ring, declaring that they will bring destruction to whoever owns them.

Loki gives the treasure to Hreiðmarr as compensation after the accidental killing of Hreiðmarr’s son Ótr. Hreiðmarr’s son Fáfnir murders him for the hoard and becomes a dragon guarding it. The hero Sigurð later kills Fáfnir and acquires the cursed treasure, linking the ring to the wider tragedy of the Völsung family.

The ring is called Andvaranaut, often interpreted as “Andvari’s precious possession.” Hreiðmarr receives it, and Fáfnir later takes it, but Andvari is the original owner and the figure who places the curse on it. It should not be confused with Odin’s ring Draupnir, which multiplies itself.