Shadow Realm

Shadow realms in The Secrets of the Immortal Nicholas Flamel are used to describe the dimensional homes that some of the Elders have created for themselves to live in seperate from humani. Typically, a Shadow Realm is usually the home of one particular deity, or that is the concept that has been seen so far with some of the Elders within the series. The goings on that occur in one Shadow Realm can effect the Shadow Realms around it. For example, when Hekate's collapsed, two other Shadow Realms collapsed with it.

Shadow Realms that have been seen in the series

 * Hekate's Shadow Realm - Before it was destroyed by the power of Excalibur, the Sword of Ice, Hekate's Shadow Realm was a lush forest in which Hekate resided. Her actual home was Yggdrasil, the World Tree, which had been raised by Hekate from a Seedling.  It was said to support two other Shadow Realms in addition to hers.  The other inhabitants of the Shadow Realm included the Torc Alta, a boar race similar to werewolves in that they could change shape from boar to human, and Pterosaurs, an ancient race of flying dinosaur.  This Shadow Realm was destroyed when John Dee plunged Excalibur into the tree, killing both the tree and Hekate and eventually winking the Shadow Realm out of existence.
 * Asgard

Shadow Realms that have been mentioned but not seen

 * Lyonesse
 * Tierna O Nog