Apple of Idunn

The Apples of Idunn are grown only in Asgard and can only be picked by the Goddess Idunn. They are what grant the Gods their virtual immortality. They grow on a tree near the Hall of Valhalla. 

Eating an apple will permanently increase the Hit Points of the consumer by one roll of their hit dice and add your Constitution modifier. If the player is unhappy with their roll, they can re-roll the dice once but must take the second roll.

No matter what, a 1 may be re-rolled. 

If anyone who is not born of Vanir or Aesir blood consumes more than one of these apples, they will fall ill and lose a permanent 3 hit dice worth of Hit Points.