I don't seen any problem there.  The hard thing is suspecting there is something wrong with the essence shards themselves.  Once you suspect that, why not suspect the Yozis?Vanman said:My question is, how would they know to ask a demon? Do they always ask demons to questions they don't know? If they do, then maybe it's plausible. But if they don't, then what gives them the idea to ask a demon? Particularly since the demon would conceivably have the information they need?
If you come to believe that someone fouled up the essence shards, you'll find that the list of suspects who could have done it is very short.
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As an aside, I feel that some people take "anti-metagaming" too far.  (Not aimed at anyone in particular).  You'd swear that the best way to make a secret impossible to discover is to publish it in a sourcebook.  Because then people will insist the PC can't know about it, it would be metagaming!  Kidding.  Kinda.
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Most Solars know (or can learn) that ancient Solars all went crazy.  Not one or two.  Not half.  Pretty much all of them.
Solars all remember their "human life".  It was just a few months ago!  They know that they weren't quite as "emo" back then. ÂÂ
They know (or can soon learn) that they received an essence shard (or at least were imbued with some form of external power). ÂÂ
Now. ÂÂ
Before the shard, I was normal.  After the shard, beside being powerful, I'm more "emo".  Centuries down the line, all of my kind in the past has gone crazy and I have no real reason to believe this time will be different.
Hum.  Normal.  Then shard.  Then crazy.  Normal.  Shard.  Crazy.  Normal.  Shard.  Crazy.  OOh!  I know, the shard makes us crazy!  Yeah, gimme five.  Hum.
Seriously, with 150 Solars of various mental aptitude and degrees of self awareness,  two or three of them are bound to understand that the Solars are cursed within the first 5 years of their return to creation.  Sure, many will rationalize away because it's more confortable then facing the truth.  t's not within the mental ability of everyone but it's not exactly Einstein level leap of intuition either.  All it takes is good self-awareness and basic logic aptitude.