Sa Paecheon, the Devil of the Venom Hands is one of the Twelve Supreme Masters, and a former member of the Old Murim Alliance.
He claimed that Dokgo Ryong was betrayed because he had been crippled in a fight against him, a claim which Dokgo Ryong later denied in spectre form. It is later revealed that Dokgo Ryong sensed his internal injuries, and, hoping to face Paecheon at full power, decided to spare him to fight another day; However, Paecheon stabbed him with his Venom Steel Whips the moment he turned his back to him.
Some time ago, he began gathering a following, which consisted entirely of men who wanted him dead but knew they could not beat him even if they joined forces. This group became known as the Wild Dogs, as was revealed in the Wild Dogs arc.
It was revealed in Chapter 78, Wild Dogs pt 20, that at some point he fought both Goo Hwi and Yongbi, and sustained permanent injuries in the battle, which left him heavily wounded.
After receiving word that the Heavenly Destroyer's disciple was heading to Naeseonhyang, he and the Wild Dogs headed out to intercept him. After confirming that Gang Ryong matched up to the Heavenly Destroyer, he attacked and initially defeated Gang Ryong easily, though shortly afterwards, Gang Ryong used a secret technique to boost his power. In the ensuing battle, the tables were turned, and Sa Pacheon had his arm torn off in the ensuing exchange of blows.
He ends up being killed within Gang Ryong's Dark Wheel Strike after Gang Ryong recalls that the Heavenly Destroyer had mentioned the battle against him, and that Ryong had been instructed by his master to go all out if he ever met Paecheon.