Michael

Michael (ミカエル) was the will that formerly resided within the Ultimate Skill Michael. He served a relatively lengthy role in the story as an antagonist, being the leader of the forces residing within heaven. He met his end in battle against Rimuru Tempest.

Appearance
Michael, who possessed the body of Rudra Nam Ul Nasca, had an identical appearance, save for his eyes which are depicted as red in illustrations. He originally wore Rudra's full-body, black and gold outfit, but after the events of The Abyss Unleashed, he switched to a white outfit with red accents.

Personality
Michael was extremely self-righteous and believed that his way of thinking was supreme and embodied justice, befitting the virtue he represented. He was the very opposite of his host, Rudra, who believed that there was no such thing as "absolute justice" or justice that could be accepted by all intelligent life.

Prior to Obera's betrayal, Michael did not have much experience with emotions as someone who relied on logical reasoning and calculations for his decisions, taking a short while to register the uncomfortable feeling that washed over him after uncovering Obera's plot as anger. While cherishing this newfound experience, he came to believe that instead of getting worked up over every setback, it would be constructive to avoid making mistakes in the future. Michael did not like imposing his mistakes onto others, instead preferring to set them straight to avoid causing friction in his future plans.

In his final moments, Michael admits that he had long suspected that Veldanava had abandoned him, but pressed forward with his plans nonetheless all the while suppressing this suspicion in the back of his mind. For the longest time, he believed that happiness was out of his reach after failing many times to emulate the joy he felt when he was with Veldanava. As his life neared its end within Rimuru, he got to experience this long lost feeling one last time. He lived his final moments in happiness, with his only regret being leaving Feldway behind.

Background
Michael was originally a hollow ego that resided inside a skill, questioning its purpose for living after the death of its master, Veldanava. Seeking to revive him, it allied with Feldway who shared a similar goal. Finding it inconvenient that it didn't have a proper name, Feldway named it "Michael", and as a result, his ego left its skill housing and became a Manas, developing a much firmer will.

To enact their plan, Michael spent the next several centuries wresting control of Rudra's body, gradually succeeding the more the latter's soul wore out with each reincarnation. He placed the minds of Rudra's closest vassals, including his partner, Velgrynd, under his control. Upon Feldway's recommendation, Michael also formed a truce with the Insectars and their king, Zelanus, whom the Phantoms had long been in conflict with. Because of Rudra's incredible spiritual strength, Michael couldn't completely act freely and was forced to play along in his game with Guy Crimson to the very end.

At the climax of the war with Rimuru's forces, Rudra's soul was completely banished, erasing any fetters placed on Michael. He chose to retreat with Feldway, moving their base of operations to the Heavenly Star Palace.

Trivia

 * According to Feldway, Michael had a similar presence to Veldanava.