Mad Demon is a Zero Numbering skill.
A skill originating from a human in the Abyss, Mad Demon. Despite being a human, he is the only one that was permitted to have the title of Mad Demon. He released all limiters and sacrificed his own body to gain strength. In order for everyone to avoid him, it is a must for the abyss race to memorize his appearance and characteristics. The effects of the skill are so disgusting that Demons couldn't help but avoid him as well.
It is the 6th skill Kang Hansoo gains Transcendence in.
When the skill is used, the user gains strength by burning their blood to spew out great power. The pain from burning one's own blood is not small. To block out the pain, the user's own consciousness is blocked. Red aura surrounds the user and their eyes turn red. Since the user becomes unconscious in this state, the only option to stop the skill is through the destruction of the opponent that was targeted before the user has lost consciousness or if the opponent manages to somehow escape from the user.
The skill burns a considerable amount of blood and stamina rather than mana.