I've played 3 times and during the first 2 playthrough i didn't know you could left clic monsters to deal damage (and get food as vampire).
But 'thanks' to that i got a lot of negative effects as vampire and one is that i deal less damage (-1 i think). There is a card(spell) that executes monster for 1 health of your own. But when you have that debuff they are left with 1HP instead of dying. Idk if it's intended or not but just wanted to give this feedback in case it's not an intended feature!
I enjoyed it tho, very nice and fun!