Rathalos, known as 'Rioreusu' in Japanese, is a significant character in the anime series Monster Hunter Stories: Ride On. Rathalos is a large, red dragon-like creature known as the 'King of the Skies.' It plays a crucial role as the partner and mount of the protagonist, Lute. Rathalos is not only a powerful ally in battles but also serves as a symbol of Lute's growth and potential as a Rider. Their bond becomes central to the storyline, highlighting themes of friendship and adventure.