Demon Boss the at the start of the game where you just stumbled upon the Tavern and Demon Boss just runs to you?
Cause if i can defeat him it surely is a knab for me cause the extra skill point!
Yup. Took alot of time (approx. 35-40 minutes) of saving and re-loading a save state to basically get critical attacks (because RNG in this game is very unforgiving).
Use bind up to heal, and try to save and reload a state if the Demon inflicts massive damage onto you (you may even evade its attacks). In the end, you'll get 300 extra coins, a stat point and some rewarding dialogue.