Perkūns, the thunder god, is named (with Patrimpo and Patollo) among the three idols set in the holy oak of Romuva in Grunau's chronicle; the historicity of the Romuva sanctuary is debated, but Perkūns himself is a securely Baltic deity. The Old Prussians were a West Baltic people Christianised by the Teutonic Order; their language died out by the 18th century.