The Thorium Devil from the Demonic Realm of Darkness and he is a high peak-level Saint. He is encountered on the 9th floor of the Necropolis of the Gods in the Southern Sea. He attempts to deceive the Saints so he can steal their souls, but he fails and attacks them. He is killed by Fain without doing any damage at all and Fain takes his Pearl of Life.
When disguising himself, he appeared as a handsome pale-skinned youngster who wore clothes made out of leaves and a straw hat. When he fails to trick the Saints, he reveals his true form. He first appears as a silver figure with battle armor, but constantly changes his shape throughout the battle.
The Thorium Devil has a body made of high-class thorium. Thorium is highly elastic, allowing him to transform into all sorts of shapes and bond with other materials easily. Elemental (with the exception of lightning) and physical attacks are largely ineffective against him unless they are strong enough to make the thorium in his body reach its endurance limit. However, the Thorium Devil is vulnerable to lightning-type attacks and techniques from the Four Edicts. When bonding with other materials, he can increase or decrease some of his properties (like size, endurance limit etc) depending on what and how much he fuses with, but he might also make himself more vulnerable to certain attacks. For example, the Thorium Devil was killed as the seawater he bonded with amplified the power of Fain's lightning technique.
Pearl of Life - allows him to recover from all physical damage and most elemental damage near instantly, which when considering his viscous form makes him even harder to injure.