OK, on another forum (warboards), some modder made a dweb that you could not cast spells under, and an AoE restore (that cannibalized maelstrom).
That person is now gone, and I don't have the mod files (must have lost it when I reinstalled Windows).
Anyone know how it could have been done?
None.
I vaguely recall seeing this too. IIRC, it was via plugin/scripting.