Q 647: Not exactly a simple rules question, but rather a "how best to do this?" question.
If you were making a Scandinavian setting, utilizing the concept of the 9 worlds (Asgard, Alfheim, Vanaheim, Midgard, Jotenheim, Nidavellir, Svartalfheim, Muspelheim, and Niflheim [I'm following the belief that Hel is a realm within Niflheim]), how would you fit the ethereal plane (or the plane of shadow) into this?
Specifically I want to make use of Spirit Animals (frostburn), which have a manifesting ability, much like a Ghost, and actually reside on the ethereal plane. The best I've been able to come up with is that the "ethereal" plane is Vanaheim [as we have almost no info on Vanaheim or the Vanir], which is basically a grandois mirror of the natural aspects of Midgard (much like the realm of faerie in more Anglo-saxon myths), and some of the fauna of Vanaheim can manifest on Midgard.... though they don't really realize it, as the two worlds are very similar.
Alternatively, I could just say that the ethereal plane and the plane of shadow are just transitive planes that are not actually "worlds," per se, but rather just an unseen part of Midgard itself, and is only accessible to fey or undead spirits, or via strong magic.
How would you deal with this?