Sariel

Overview
The Ultimate Skill Hope King Sariel was used by Chloe O'Bell. Its essence is 'Absolute Separation' to overcome difficult situations (for example, to cut a shield that was not meant to be cut).

Web Novel
Usurper Mathematician Infinite Prison (無限牢獄mugen rōgoku) is a Unique Skill that entombs the target in a complex number of spatial dimensions and also seals away most Skills within. It does not weaken over time. It cannot be damaged via standard Physical Damage.
 * Usurpation (簒奪 sandatsu): This main ability allows the user to 'rob' power from their opponents, effectively weakening their skills and magic. Although this ability only works on those stronger than the user.
 * Forced Usurpation (強制簒奪 kyōsei sandatsu): This is a skill that requires mastery of the Unique Skill Usurper. It grants the user the ability to 'rob' power even from those weaker than the user.
 * Copying (複写 fukusha): This main ability allows the user of the skill to copy and obtain the skills of those they are fighting.
 * Analysis: The user's analysis capabilities are enhanced.
 * Thought Acceleration: Increase the speed of the user's senses and thought by a thousand times.
 * Prediction Simulation: This allows the user to predict the paths of attacks.

Absolute Severance-Seals the majority of the target's powers. If used just right, it can even temporarily seal the powers of a being as powerful a true dragon.

Absolute Defense-Blocks all attacks both magic and physical.

Light Novel

 * Indomitable: During the events of the Light Novel, Granbell Rosso successfully obtained this Ultimate Skill by evolving his innate Skills Indomitable.
 * Life and Death Manipulation: Upon evolving and obtaining this skill during his battle against Luminous Valentine, its been stated that Granbell's Hope King Sariel had the same level of power, ability, and authority over life and death as Luminous's "Lustful King" Asmodeus.

Trivia

 * Sariel in mythology is often seen as an angel of healing and/or an angel of death.
 * Although not said in the story, it is possible that absolute severance is an evolved form of the skill, severer.