Deal with a devil a skill where you try to strike a deal with the creature chosen(you don’t need to know there language) so you roll a persuasion check to sell the deal. you can ether break the deal and kill the now soulless creature or upkeep your side of the deal

Use one hole turn to set up the pentagram and on you next turn you can use your bonus action to activate it to turn into a demon

as a demon you have advantage on all charisma rolls/checks you are hovering and you regain all your hp back as temp hit points

note:if pentagram is destroyed demonic transformation is undone

any item you pick up can be eaten but watch what you put in your mouth cause it can give you some major changes

easting red soul stones makes you a dragon for a short time

eating blue soul stones makes you a rideable cloud for a short time

green soul stones makes you into a plant 

you hit someone with your horns but you can do it in both forms

in goat form you deal 3d4 bludgeon damage plus your strength mod

in demon form you deal 3d4 piercing damage plus your charisma mod