I've been looking through the KatG box and thinking about Fthaggua. Am I right in thinking that if I have Mists of Lethe in my discard pile, I can use its action to return to my hand one of the cards attached to Fthaggua (they are, after-all, Yog cards that I control)? If so, then on paper that sounds like a good way of stopping important (dead) characters from getting into my discard pile.

What do you think?

they are, after-all, Yog cards

I think this is not the case. Insane characters which are also facedown lose their faction and just retain their title. FAQ 3.1 says that cards attached to Fthaggua don't even retain their title. I'd be really surprised if they would retain their faction...

It just occurred to me in a game that I can simply return Fthaggua to my hand and then ALL the relevant attachments go into my discard pile. Muhahaha! Problem solved. Albeit a little more expensively.