They should probably change the Frightened status to what it is in 5e instead of the complete panic mode we have in BG3 where you have to flee drawing AoO's and can't fight back at all.
Otherwise it could be a party wipe on sight with a DC 19 or higher AoE menacing attack that lasts for 10 turns.
Or the alternate, where you land one successful Menacing Strike on the dragon and then get a free round (+opportunity attacks) to wail on the dragon. Possibly doing it again next turn.
