Yggdrasil And The World's Moods

The Norse mythological World Ash Tree, Yggdrasil:

is a metaphor in Poul Anderson's Technic History/Dominic Flandry novel, A Stone In Heaven;

exists literally in Anderson's myth-retelling heroic fantasy novel, War Of The Gods;

exists in one of the many parallel universes in Anderson's Operation Luna.

We can handle any of these options but can we conceptualize a single universe that somehow incorporates every mythology? In Neil Gaiman's The Sandman, when Lucifer Morningstar retires as Lord of Hell, he expels the demons and damned, locks the now empty Hell behind him and gives the key to Morpheus, Lord of the Dreaming. Various pantheons petition Morpheus to give them Hell, including Odin who hopes to survive the Ragnarok by sheltering in Hell! In Lucifer, Mike Carey's sequel to The Sandman, Lucifer visits Loki bound under the Earth. We read:

Lucifer: "There is a cavern at the heart of the world..."

Mazikeen: "Is there?"

Lucifer: "Sometimes. It depends what mood the world is in."

-Mike Carey, Lucifer: Inferno (New York, New York, 2004), p. 134, panel 2, captions 1-3.

Well, that explains everything. Cosmology changes with the world's moods.

All of these works are connected in the collective imagination.