Just the usual damage methods. The party includes a monk, a battlemaster, a wizard, a cleric and a bard. There were multiple crits on the party side since they had advantage on most attacks due to the combination of PC abilities. The dragon never got its breath recharge, and like I said, my dice were cold and the PCs' were hot (except the poor monk).OP mind me asking how the PCs were killing stuff?
Controls great but imho it's the others who tend to seal the deal.
Again, one of the worst things a GM can do in my opinion is start an arms race with the players, and punishing them for success is just as bad.Just add 3-5 Kobold sorcerers to your next boss fight to cast suggestion on the PCs/counter the suggestion spells they cast.
That said, the dragon's lieutenant looking for revenge will definitely acquire something that grants protection from charm/mind control first.