In D3 there are 17 prime material planes (see list on the right). There once existed an 18th but that was consumed to preserve the balance of the worlds. The Nature plane is your standard AD&D plane, the others are particular scenarios, with increased difficulty and peculiarities. All are linked to a general cosmology of the planes, which includes both standard inner planes, and the outer planes (though with some variations within the normal AD&D).

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