The dwarf turned to stone by Thor after a riddle contest was Alvíss.
In the Poetic Edda poem Alvíssmál, Alvíss arrives to claim Þrúðr, Thor’s daughter, who has apparently been promised to him in marriage. Thor objects to the match and challenges the dwarf to demonstrate his supposedly exceptional wisdom. Rather than fight him directly, Thor keeps asking questions about the names used for natural things by gods, humans, giants, dwarves and other beings.
The exchange lasts through the night. Alvíss answers every question, but Thor has deliberately delayed him until sunrise. As daylight appears, the dwarf is exposed to the sun and is petrified. This detail reflects a common Norse mythic motif: dwarves are associated with underground darkness and may be harmed or transformed by sunlight.
Alvíss means “All-Wise,” and the poem is especially valuable because its riddles preserve variant mythological terms and poetic vocabulary. He is not the same dwarf as Andvari, the owner of the cursed ring, or the brothers Brokkr and Sindri, famed for forging divine treasures.