Kiara Sessyoin

Kiara Sessyoin (殺生院キアラ) is the Master of Caster in Fate/Extra CCC and the game's true antagonist.

Background
She is also a master who participated in the Moon Cell Holy Grail War. She is the reason that BB was unleashed, when she interfered with Sakura Matou's program.

Appearance
Her attire resembles that of a Japanese Buddhist nun; she wears a tight dress with a slit up the left side exposing her leg. After consuming both Passionlip, Meltlilith, BB and Sakura her appearance changes to a demon.

Prologue
When Kiara was first introduced, she assumes the role of Taiga Fujimura; the homeroom teacher of Hakuno Kishinami and Shinji Matou.

Chapter 1 - Backyard of Eden
After Hakuno shifted to the Far Side of the Moon Cell, Hakuno was tasked to recruit other Masters to join the Student Council and encounters Kiara, who claims to have lost her memories. Kiara tells Hakuno that she has no interest in joining the Student Council, and reveals her servant Caster and refers him by Andersen. Andersen then warns Hakuno not to trust Kiara.

When Hakuno collected all the SG information from Rin Tohsaka, Kiara helps Hakuno to enter Secret Garden to find and face the real Rin.

Chapter 5 - Iron Maiden Princess
Later in the fifth chapter, Kiara starts showing puzzling behaviour such as making herself busy whenever Hakuno tries to make contact with her.

She is seemingly killed by Meltlilith when she sneaked up behind Kiara.

Chapter 7 - I Love You
In the True Route, she reappears when Kiara first absorbs BB when she couldn't control Moon Cell system. Andersen reveals that Kiara absorbed Passionlip's Ego allowed her fool everybody with her fake death. She traps both Hakuno and their Servant, and used this opportunity to absorb Sakura and fully control the Moon Cell. Caster used Marchen Meines Lebens to allow Kiara to be reborn as the earth mother goddess and reach a state close to that of a True Demon. Caster sends both Hakuno and the Servant to two different locations.

Hakuno confronts Kiara in her Heaven's Hole form. To her surprise, Hakuno's Servant arrives to fight. Normally, no normal human could stand against her but she lost to Hakuno due to the girls that were absorbed, wanting to protect their love for Hakuno and resisted inside her body. Caster scorn her, calling her an idiot that charged right into the fight with no regards to that one weakness. She dies saying that she was not defeated by a Hero nor a Savior but by women like her.

Fate/Extra CCC Fox Tail
Kiara was killed off by Saber and Kazuhito Sakagami.

Abilities
Gojyou Shinkan is a codecast skill that allows her to access someone's Secret Garden.

Combat
With Kiara absorbs Passionlip, Meltlilith, BB and Sakura Matou and through Caster's Noble Phantasm and the Moon Cell, she reaches a similar existence to a True Demon. Her existence is similar to a certain man-made demon who had once been demonized and celebrated as a sacrifice to prove the evil of mankind. She becomes known as Heaven's Hole and gains the Noble Phantasm Angra Mainyu/CCC. While Caster is unsuited to fight, Kiara personally fights with close combat.
 * Taizōkai Riken-in (胎蔵界　理拳印) - She makes several hand seals to use this self applied skill. It grants enemy's ATTACK skill sealed, HP absorption effect to GUARD and stun effect on BREAK.
 * Kongōkai Chiken-in (金剛界　智拳印) - She makes several hand seals to disable any attacks and causes MP damage.
 * Dai-zushi Chiya kan pō - She creates an energy orb from her hands; as the orb levitates, it fires energy rain on the enemy and causes damage.
 * (詠天流・四念回峰行) - Causes damage and paralysis.