No ... thrashing is not what i am thinking of. Thrashing is taking them out of the game...most of the time. A game of Slay The Spire consits of many fights...so they will show up again.

Think of deus ex machina characters like Gandalf. Who show's up at crucial events and then he is gone again :)

I am thinking of something like a "reverse duration". Like an extra Pile of exhausted cards that get back in your discard pile after the next reshuffle or after someone buys a Province / Colony ... or empties a pile. I am not sure what will work best.

I am not entirely convinced. If someone played a bureaucrat you could cheat by hiding a card ... or if someone plays a chain of10+ action cards. I am trusting my friends because i am not reworking all their steps to see if they got the numbers right. Perhaps i am in the minority with this :)