Kerbec

Kerbec (ケルベロス, Keruberosu) is a Etherious demon that was created by Zeref over 400 years ago. He was eventually found by Mard Geer who decided to make him a somewhat guard of the guild he was creating. Though not part of the Nine Demon Gates, Kerbec was still actually pretty powerful. So instead the Underworld decided to make him his personal guard. Eventually though he was banished from the guild and nearly destroyed by the Ice Devil Slayer as he was different from the others. Like Zeref, Kerbec had began to value life which Mard decided would be punishable by death.