Sphere of Wonder

This spell calls into being a stationary sphere of magical radiance equal in effect to a light spell, in which no spells or magical item discharges can take effect (or persist, if already in effect) except those of a type silently chosen by the caster during spellcasting. For example, the caster could choose to allow only spells involving fire to function, or only electrical discharge magics (such as lightning bolt). The prohibition cannot be narrowed down to allowing only a particular spell (for example, to allow fireball but not flaming sphere is not possible), but there is no way for beings other than the sphere-caster to tell what spell type works except by trial and error.

Spells of the wrong type cast into the sphere from outside are negated at the point where they touch the sphere. The magic has no effect on beings or items once they leave the sphere. A rod of cancellation brings the sphere down instantly.