Magic and Mystara
by HåvardIf the Nucleus of the Spheres (NoS) is the source of all magic on Mystara, how were people able to cast spells in the Age of Blackmoor? Were they able to tap directly onto the true source of magic back then?
Magical energy is derived from the Spheres themselves and permeates the Multiverse. The Sky Shield has a special effect on magic, not unlike that of a greenhouse, allowing more energy from the outside to be let in, but not letting anything out. This makes Mystara more magical than most other worlds in the Prime Universe and the entire Multiverse. The main effect from this is that creatures with magical abilities are much more common here than elsewhere.
The NoS is a device created to enhance magic cast by those who know how to access it. Its power is also drawn from all of the Spheres. However, the curse placed on the NoS by Noumena made sure that for every time the NoS was used, magic was drained from Mystara. This drain would eventually be so big that more magic would be lost than what would be gathered from outside the Sky Shield. Eventually, Mystara will be left without any magic at all. This will make spellcasting impossible and permanently deplete all magical items. Furthermore, magical creatures depend on the presence of at least some magic to exist, much like most creatures depend on air. So once Mystara is fully depleted of its magic, these creatures will suffocate and die unless they are able to leave that world.
Of course, as long as the NoS is used wisely, or the curse is lifted (altered) things should be fine.
The magical Blackrock of Blackmoor may not have been the source of magic in that era then, but trying to reconcile part of Cthulhudrew's suggestion, perhaps the Blackrock was a magic enhancer not unlike the Radiance?