We´ve always had the option to use higher rarity books on lower rarity champs, so my money would be on true, not all my money but some

I need lego books and can easily grab the 2 myth books on summon rush.  But, if they wont work on Legendary then they are a waste to me.  At least for now.  

It'd be a waste if they do work on a legendary. I'm sure they do, but under no circumstances should anyone use them for that unless they are like a Saudi prince with more money than common sense and an unhealthy addiction to giving Plarium more money than they deserve.

Definitely do not use Mythical books on Legendaries. They'll work on Legendaries, but you don't want to do that. :)

Don't do either. 

Don't do this event

Absolutely do not use red books on legos

I don't know where Mythical books will settle in value and scarcity but this. intuitively though it just seems like the answer is very high to both

I would probably be holding shards now too, as we don't want to be caught low on resources incase upcoming fusions are good. 

Mythical Cadaver fusion when Davey?  

Already exists my good man, he already exists. 

don't understand why but two accounts and no free myth shards!!!