Psycho Mantis's parents were a couple who lived in a village. They had a son together.
The mother died in giving birth to their son. From then on, the father hated him. The young Mantis, who discovered this while diving into his father's mind, which was also the first time he did so, became terrified that his father was going to murder him.
This revelation caused Mantis to burn his village down, killing his father, which caused Mantis to fall unconscious.