Razen

Razen (ラーゼン) was the Chief Sorcerer of the Kingdom of Falmuth and oversaw it's many otherworlder summonings, but after the events of Demon Lord Awakening he serves Diablo as his faithful servant.

Personality
Razen is a prideful individual who believes he's one of the best sorcerers there is. But he's also wise and knowledgeable enough that he knows that there are many opponents that even he could not beat.

Like many in Falmuth, Razen is shown to be extremely selfish and cruel, happily summoning and enslaving people from other worlds, only to later sacrifice them to increase his own power, made worse by the fact he destroys their souls rather than simply killing them.

Despite these negative qualities, he is fiercely loyal to those whom he pledged his loyalty towards. He served the Kingdom of Falmuth for hundreds of years, and begged Diablo to spare King Edmaris even at the cost of his own life when they were turned into chunks of living flesh by Shion. After submitting to Diablo, he worked hard in helping Youm Farmenas to run the newly established Farmenas Kingdom, even willing to oppose his master Gadra when he visited in Volume 12.

Background
Razen is a brilliant sorcerer who has served many years as a Court Mage in Falmuth, part of why he has lived so long is his Possession Spell. He was once a student under the Great Sorcerer Gadra.

Demon Lord Awakening Arc
Razen attacked the Jura Tempest Federation together with his nation but realized too late how powerful his enemies were. He possessed Shogo Taguchi's body after saving him from Geld and thought that with his abilities he could put a fight against a Demon Lord. However, after surviving Rimuru's Megiddo attack thanks to his new Unique Skill Survivor and seeing the devastation of Falmuth's army he realized he could never defeat Rimuru so he tried to escape with King Farmus but was instead captured alive by Diablo.

The Octagram Soars Brightly Arc
Razen has fallen under the effect of Diablo's Unique Skill Tempter, which makes him unable to disobey Diablo's orders. He gets tasked with assisting Diablo and Youm with the scheme of taking over the Kingdom of Falmuth and effectively turning it into a puppet nation of Tempest.