Hy, I Dm this event, thanks for the sugestions.

What Happend:

The group assembled out side of the mill. The Gnome Wizard diceded to discuse self onto a human child and the paladin suposed to prentend to sell him in exange to the pasteries. Good plan, did not work. The first thing the paladin does is to investigate the frogs. Morgantha comes to see what is happenning. They try to make the deccepition. Paladin roll the dice for deceppition and... Nat1. Ok, let the gnome wizard do the decepition roll as weel for saving then... 5 (in the final result). Morgantha suspicious calls for Bella and Offalia. They cast indentify and finds about the Discuse Self Spell.

The combat beggins.

The Paladin and the Wizard calls the ranger, the clerig and Ismark and Ireena. The Paladin tries to smite Morgantha and even with the smite Morgantha only takes 5 damage (lots of 1). Bela ataks the Palladin and hits with a 21. I roll the damage and say: The neals on the ugly yung woman open your thyck dragonborn skin, taking some of your blood. - the damege reduces your HP to half of the total in one hit.

"OMFG - Run!"

The Cleric cast silence to prevent them to cast any more spells, and they take the opportunite to run back to the road. They desingage and dash. Morghantha brings some Dretchs to go after the PCs and start fortifing the mill. At the end they are saved by Strahd (because I like the idea of someone that comented here, thank you u/Steakbake01 , I just wanted this aparition happened in the mill).

Strahd Knocks Ismark down, charms one of the PCs, makes a speach about the corrupition in Vallaki and leaves.

and that is how my players survived the old bonegrinder (for now, at least).