His left eye allows him to see, hear, and talk to the dead souls in the Soul Dimension. When uncovered, it affects his depth perception, makes him feel cross-eyed, and become overwhelmed.
Marks start spiraling from the left side of his chest. They start under his skin and can appear unintentionally due to emotions and anxiety. These marks can surface and harden working as armor.
Astuno can grow horns and wings due to his demonic heritage. He gains enhanced strength and speed, and be able to put them away. Though may be painful to come out.
He's able to intentionally fall into the ground and enter the soul dimension. This allows him to attack by flying,falling, or jumping 'into' the ground like a fox. This, however, can be disorienting if not trained.
+ He had the ability to have souls come out of their dimension under his rule. His solidified marks were originally designed to work as a portal for them. They'd act as a horde that only worked in shadows where he could hide and Dimension hop. This could still work but I forgot about it.