The boy awakens in a ruined castle in a deep valley known as the Nest. He discovers an enormous creature called a Trico, chained and wounded. Though Trico is hostile, after the boy removes the spears from its body and feeds it, it begins to accept him. The boy unchains Trico and they explore the area, discovering a mirror-like shield that summons lightning-like energy from Trico's tail. The pair make their way through the castle ruins, evading the ghostly soldiers, while Trico's broken horns and wings slowly regrow.
The player controls an unnamed boy who must cooperate with a griffon-like creature to solve puzzles and explore areas. The boy can climb on structures, carry objects such as barrels, and operate mechanisms such as levers. Trico's size and agility allow it to reach areas that the boy cannot reach alone, and fight off guards who attempt to capture the boy. Conversely, certain obstacles, such as gates, or glass eyes that frighten Trico, prevent Trico from progressing, and must be removed by the boy. The boy must locate barrels to feed Trico when it is hungry, pet Trico to calm it after a battle, and remove spears thrown at Trico by enemies.