Forget all this mystical cock about Illumination (like it being some transcendental watchamacallit). Think of Illumination as being the realisation that everything you've been told isn't quite as black and white as you thought.
Real world examples of this (in order of increasing improbability):
This makes Illumination quite an "enlightened" view for the types of culture found in Glorantha and therefore well alien and something to be feared by most people. Glorantha is a world of dogma: Anything that breaks the dogma is going to be contentious and be feared.
What makes the Lunars unique is that they're not quite so dogmatic (they're dogmatic about not being dogmatic) and embrace most things if they can find a spare hole in the mythology to stuff it in. They're already half Illuminated by this. Of course, this is probably just Lunar propaganda. After all the Orlanthi have managed to live for several million years doing things just so which is undeniably right...
Bang a gong and say "Om",
Ash
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