Mariabell Rosso/Chronology

Saint-Monster Confrontation Arc
Mariabell is revealed to be the granddaughter of Granbell Rosso, who was manipulating the Clerics of the Seven Luminaries behind the scenes.

Majin Behind The Scenes Arc
After the failure of Duke Muze during Tempest Federation's opening festival, Mariabell decided to invite Demon Lord Rimuru into Council of the West and set him up into a trap. However, this plan also ended in failure.

Deciding that things are only going to get more dangerous as time passes, she decided to personally move out and eliminate Demon Lord Rimuru believing herself to be the stronger one. Unfortunately for her she failed to realise that Ultimate Skill users like Rimuru were completely immune to her unique skill, and was defeated by Rimuru in their battle so she tried to escape. However, she was confronted and then killed by Yuuki Kagurazaka.