Carl is your friend. He is a traitor, willing to sell out his friends. But you are his best friend. He's evil, selfish, smart, malevolence and greedy. He found a way to turn the soul of the deceased into a demon and used himself as a vessel to make a deal and gain greater strength and immortality. He uses your soul because you died and were his best friend, and because you was his best friend he believed that you would accept his summons. You're a soul and only he can able to see you and touch u