Well this is getting pretty interesting. And leads me to a rules question as I plan my next turn:
What happens if I make a mirror and use Quince’s midband to make it a copy of your Justice Juggernaut (yes, mirror Juggernauts are all the range these days, it seems)? I’m supposed to trash the mirror at the end of the turn, but JJ has 2 lives. Does that mean the mirror survives? I guess so. But is it still a copy of Juggernaut, or is it a plain ordinary 0/1 mirror? (From my own reading of the card texts, I think it will stay as a Juggernaut, with a crumbling rune of course, but I’m not certain.)
Oh hang on, I think I remember reading somewhere else that trashing something doesn’t cause it to “die”. So the mirror would still be trashed? Does anyone else with more rules knowledge want to weigh in here?
(Although, I’ve just realised I can’t spar with my own mirror without killing it, so the play I was planning is less impressive than I thought anyway 
)