Will M. Baker
since Guardians can only be removed from the hall thru 'defeat', is it immune to CD? Is CD considered as a 'defeat' card?
Only the Dark Champion and Death Sentinel have this text; other guardians do not (though once in Rank 0, I think this is true of all guardians). If a guardian's (or monster's) health is reduced to zero, I would consider that a defeat. I think this text is just trying to say, "You can't lose to the monster to get it out of the hall, and neither can you banish it to get it out of the all."