For a concrete example, say it is the Silver Campaign level, but you have Copper Eldritch Monsters.
The level boss is a Master Sorcerer. Is he Silver or Copper?
Is the Level Boss for each level the campaign level or the monster upgrade level?
The Level Boss does not get a free upgrade based on the campaign level. So in your example, the Master Sorcerer is still Copper.
Big Remy said:
The Level Boss does not get a free upgrade based on the campaign level. So in your example, the Master Sorcerer is still Copper.
Well, to be fair, it could be an upgrade or a downgrade, but I take your point.
LOL
True, for Eldritch it would definitely be a downgrade if they are still Copper at the Silver campaign level.