hmmm... it's tricky... maybe there's some oversized bitmap textures some places?

Maybe try turning off all shadow receiving, shadow casting and self shadowing off on ur orb textures and the volume texture? then apply a procedural map to the light inside the orb if neccesary to display some light patterns that look like they come from the orb. If the orb is supposed to light the scene there's no need for it to go and be receiving all kindsa shadows anyways.

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