Ost Horai


 * This article is about the character. You may be looking for the anime episode or manga chapter.

"No. I was fated to destroy life, to be hated and scorned. People were to cheer when I died, and yet here you are, sad to see me go. I cannot help but feel joyful."

- Ost

Ost Horai (オスト＝ホウライ) is the soul of the Spirit Tortoise (霊亀), one of the Four Guardian Beasts. She is the manifestation of the Spirit Tortoise itself, in its humanoid form.

Appearance
Ost has shiny brown hair tied into a chignon with flowers and sharp, Chinese-looking eyes.

She wears a green Chinese-style dress with a hexagonal pattern resembling a turtle shell. She also has a loose shawl wrapped over her and is attached to her dress at the waist with lotus flowers. Her skin is healthy and bright and according to Naofumi, she looks vivacious.

Personality
Ost is kindhearted and will sacrifice whatever is needed to protect her friends. She cares more about the lives of others than her own, and is prepared to give her life to save others. She wishes that she could have lived a life as a normal human and spent more time with Naofumi as an ally, but doesn't let this desire get in the way of defeating Kyo.

It is noted that her first method of calming the waves is to use her beauty to bring about war and harvest the souls for the purpose of keeping the world safe. Had that failed, she would release Spirit Tortoise familiars to speed up the process, only opting to bring about the Spirit Tortoise to forcibly gather souls required if all other options were exhausted. Because of this, it can be assumed she is capable of manipulation and cruelty, a side of her Melromarc's Queen is quite familiar. However, this is not her real personality: it is act she puts on as part of her mission to protect the world. She doesn't display any of these traits in front of Naofumi's group since her purpose had been usurped by Kyo and she had no reason to.

Despite considering it a necessity to save the world, Ost carries a great deal of turmoil over her actions. Her greatest regret and fear is that having to play the villain would end in her dying hated and alone. She is happy that she got to meet Naofumi's party because they gave her a place where she could be herself even though the cause was decidedly negative.

Abilities
Ost mainly uses earth and support magic, along with magic long forgotten by humans. She can also manipulate gravity fields around herself, allowing her to cast gravity magic as an extension of said ability. As the soul of the Spirit Tortoise itself, she can halt the movements from other Spirit Tortoise familiars and take energy from them to fuel her own spells. She also grows in power the deeper she goes into the Spirit Tortoise, allowing her to recover from wounds as fast as the beast does. However, she cannot control the main body of the Spirit Tortoise due to it having been taken over by Kyo.

Magic
It makes targets float. Greatly increases strength. Increases the defensive radius and abilities of Naofumi's shield while maintaining said magic. It replenishes the target's SP. Nullifies SP Drain effects. Effectiveness decreases with repeated casts. Produces black orb that shoots towards enemies, creating an field of intense gravity that pins them into the ground upon a successful hit. Shoots a blazing inferno from Ost's hands that burns enemies. The flames have the same properties that Dark Burning Curse has. it's powered by the shield of wrath, extending the time Naofumi can use it by using up the rage inside it. However, it also damages Ost, covering her hands in horrible burns. This spell shoots a large diamond spike from Ost's hands.
 * Gravity Reversal・Float「重力反転・浮遊 Juuryoku Hanten Fuyuu (lit. Gravity Reversal - Float)」
 * Herculean Strength「金剛力 Kongouriki (lit. Vajra's Strength)」
 * Unnamed Holy Weapon Ability Increase Magic
 * Soul Light「魂光 Yuukou (lit. Soul Light)」
 * Drain Seal「ドレインシール Dorein Shiiru」
 * Gravity Field・Extreme Gravity「重力場　超重力 Juurikijou Choujuuryoku (lit. Gravity Field - Hyper Gravity)」
 * Black Dragon Flame「黒龍炎 Kokuryuuen (lit. Black Dragon Flame)」
 * Drifa Diamond Missile「ドライファ・ダイヤミサイル Doraifa Daiya Misairu」

Cooperative Magic

 * All Liberation Aura「アル・リベレイション・オーラ Aru Tsuvaito/Ribereishon Oora」

Ost once assisted Naofumi in producing a stronger version of Zweite Aura before he learned to use Dragon Vein Magic.

Anime Exclusive Magic

 * Ultra-Gravity Enhancement: Sinking Temple「超重力強化　沈殿 Choujuuryoku Kyouka Chinden」

Produces a translucent black orb that spreads over a large area, creating an field of intense gravity that pins enemies into the ground.

Background
Ost was active even before the Spirit Tortoise was unsealed and on a rampage. As part of the Guardian Beast, she was supposed to be a backup to fight against the waves in case the heroes failed or weren't strong enough. However, Guardian Beasts are considered a last resort since they fulfill their terrible role by sacrificing roughly 2/3rds of living creatures in their world.

Ost's specific role was to "pave the way for the Spirit Tortoise's awakening." She was to manipulate countries into going to war to create sacrifices in case the Spirit Tortoise had to be unsealed. She was also to supply hints to the Heroes about how to break the Spirit Tortoise's seal if needed.

Volume 6
After Naofumi receives word about mysterious monsters across Melromarc, Ost appears to Naofumi, pleading for him to kill her before "she" goes on a rampage. However, her appearance is brief and cryptic so Naofumi decides to ignore her pleas.

Volume 7
With the Spirit Tortoise being defeat for the first time, Naofumi starts cleaning the streets of the Spirit Tortoise familiars. However, this time Ost was able to manifest herself and stay permanently. She warns him that the Spirit Tortoise is not actually dead and that it will revive again. As Naofumi receives word about the Guardian Beast's revival, he then introduces Ost to Queen Melromarc and her forces. Ost provides all the information she has on the Spirit Tortoise's body and then supports Naofumi and his party who were trying to slow it down from destroying Melromarc.

When Fitoria arrived to confront the Spirit Tortoise herself, Ost joined the expedition party to travel inside the Spirit Tortoise. Working in tandem with Fitoria, the two groups are able to destroy the heart and the head at the same time which permanently kills the Spirit Tortoise. Naofumi's party, including Ost, then head further into the Spirit Tortoise to see who is responsible for the terrible catastrophe. In the core of the beast they find Kyo who had stolen the energy that the Spirit Tortoise had collected during its rampage. They fight him and are almost overwhelmed. At Ost's final wish, Naofumi used the Spirit Tortoise shield she had unlocked to destroy the Spirit Tortoise's core and defeat Kyo. Kyo, seeing that he was defeated, escaped to his world with the Spirit Tortoise energy he had collected. However, the Heroes rush to Ost who is slowly fading away due to her core being destroyed.

As she lays dying, Ost tasks the heroes with reclaiming the Spirit Tortoise energy that Kyo had stolen and then used her authority as a Guardian Beast to allow Naofumi to travel between worlds. After a tearful goodbye, she fades away.

Volume 16
After Naofumi was mortally wounded by Takt during his ambush, he was able to commune with the Spirit of the Shield in his near-death state. Within his shield, he found Ost and Atla who spoke on the Shield's behalf. They warn him of the "World Eater" behind the waves and then offer Naofumi the option to bring him back to his original world, which he refuses. During their conversation, Ost hints that there is a way to bring her back to the world of the living, but she is perfectly happy in the shield. After their conversation, Naofumi wakes up from his unconscious state, and later discover that he can "communicate" with Ost and Atla through the glowing gem on his shield.

Naofumi Iwatani
Ost sees Naofumi as the only competent Legendary Hero that had been summoned. She sought his help to help destroy "her" body, which he eventually agreed to do. Ost proved both useful and selfless during their time together and she gave Naofumi many gifts, including learning about Liberation-class magic and the ability to travel between worlds. Naofumi thoroughly appreciates the sacrifice she went through to save the people of Raphtalia's World and was sad to see her go. He mentions that if he could resurrect people, he would bring Ost back in a heartbeat.

Mirellia Q Melromarc
Ost and Mirellia had briefly met each other before the Spirit Tortoise catastrophe during a world conference. At that point, Ost was manipulating one of the kings present so Mirellia had a terrible opinion of her. However, Ost proved herself and Mirellia became more cooperative.

Trivia

 * In the English version of the Light Novel, her hair is described as having a red color. That is likely due to the case that the term "紅茶色" was used for her hair color, which can be translated as black tea color. But because "紅" also means red, the hair was translated as red-colored.
 * Her first name comes from the German word for east (Where the Spirit Tortoise came from), while Horai is the Japanese name for Mt. Penglai, the mountain carried on the back of the Spirit Tortoise.