Idunn

Idunn (in some versions Iduna) is the Norse Aesir goddess who acts as the keeper of apples that grant her fellow gods eternal youthfulness.

Magnus Chase and the Gods of Asgard
Magnus encounters a pigeon (actually Utgard-Loki in disguise) that tells him Samirah al-Abbas, Blitzen, and Hearthstone that he knows how to get the Sword of Summer, but he wants something in return: Idunn's apple of immortality. To get the apple, they will need to attract the sea goddess, Ran.

Trivia

 * Her name is traditionally spelled Iðunn.