

Which explains why it was mentioned in the monster entries for shadow dragons in 1st edition (pp.58-59 of the Monster Manual II mentions "planes of dimness such as the Shadowland"), 2nd edition (p.85 of the Monstrous Manual), 3rd edition (p.44 of Monsters of Faerun), and 3.5 (p.191 of the Draconomicon).


The Plane of Shadow (whatever the nonce name it changed a lot but was always identifiable) has been a part of the standard cosmology since 1980 (1e Deities & Demigods, p.114). No, the "Plane of Shadow" is way older, but the "Plane of Faerie" isn't.
