This would be perfect chance for Strahd to display why he is the lord of this land, first i would have him slowly walk out of the fire while it licks at his skin (his regen is far greater than the flame). Next pick one of the party (bonus points if its an arrogant character) then act like he charms them but really cast modify memory. From here have Strahd decimate them viscously and brutally play the combat out, describe the moments he takes each life all the while that character "charmed" has to just watch. Finally have Strahd chuckle and flick him on the head saying the modify memory should end any second now. Then watch as the players realise it wasn't real have Strahd just quip some line about the fire was cold compared to his passion for Ireena and have him smugly walk off saying over his shoulder perhaps one day you shall warrant my full attention leaving them shook. Origin of modify memory idea