Well, Greg has said the answer to the GLS is in Glorantha 2 on page 18 so I'll be buying it just for that reason.
The secret is very important to me as a gamemaster because I always want my players in the heart of the story, not bystanders witnessing others grand events. my players are the deciding elements in the unfolding of all these events. Naturally I NEED to know what the Secret was that got the GL's destroyed because eventually, my players will be caught up in the middle of it and to even begin to plan such a campaign I'll need to know this ahead of time.
I'm still trying to work out if the God Learners destruction should be portrayed as a tragedy instead of being the evil bad guys getting their just rewards, Perhaps the Secret is something the world NEEDS to know, but the God Learners screwed it up because many of them were just plain greedy and so the God Learners Secret, which could have proved the salvation of man, is lost.
Perhaps Argrath finally learns this secret and that is how he sets free the world?
Veering slightly off topic: One thing that has just recently occured to me and if you'll read my post under the thread "Spells" you'll see my outlook on how Runes interact with the real world and create magic and you'll see I postulate that all three classes of magic, sorcery, spirit and divine, approach how to access Runes and use them from different angles, but ultimately, all magic comes down to knowing the Runes. So a sorceror teaches himself Rune knowledge. A theist gets powers from Runes from his God. If he attains Rune Lord status, he KNOWS the Rune himself and no longer needs its powers granted to him from his God, he can initiate those powers himself, thus the spells become reusable to a Priest/Rune Lord. A shaman finds a spirit that knows the Runes and gets that spirit to cast the spells.
Well, what occured to me is that Arkat and the first cycle of destruction occured because Arkat went the Theist route to exploiting Rune knowledge, he went from cult to cult, gaining Rune Lord status and as soon as he had that cults Rune knowledge for himself and no longer needed the cults God, he jumped to another cult. what he knew was that once the God had given him the knowledge, it was his to keep. He learned the Runes for himself. What the God Learners did was to steal these secrets from the Gods. This was the second cycle of destruction. 'They took the sorcerors route to exploiting Rune knowledge. In the 3rd Age, Argrath completed the third cycle of destruction. Was it someone(s) taking the spirit magic route to exploiting Rune knowledge that caused the Great Illiteracy? There's a certain symmetry there when you think about it. We know what happened at the end and how the Trickster was fundamental in betraying the Gods and changing the world. It seems on the surface to have been one more instance of God Learnerish disrespect for the nature of HeroQuesting. It seems on the surface to be very theistically driven. Yet I can't help wondering if a spirit magic route to exploiting Rune knowledge couldn't somehow be used to explain the repurcussions, if only to lend that symmetry to the whole history?
In any event, after the 2nd age, the rules changed. After the 3rd age the world changed, it became more 'earthlike'. Perhaps this is all part of the Grand Design. To understand if that is so, one would HAVE to know what the God Learners Secret is, just to be sure the announcement of the secret wouldn't render such a Grand Design theory impractical or screw up any other possible explorations a gamemaster might want to make into the nature of magic, the magic of nature (in Glorantha) and all points in between..