Kischur Zelretch Schweinorg

Kischur Zelretch Schweinorg (キシュア・ゼルレッチ・シュバインオーグ) is one of five living Magicians capable of True Magic beyond modern science or Magecraft. He has numerous nicknames, including Zelretch the Wizard Marshall (魔道元帥ゼルレッチ), Zelretch of the Jewels (宝石のゼルレッチ), Old Man of the Jewels (宝石翁), and Kaleidoscope (万華鏡（カレイドスコープ）)." He has control over the Second Magic, "Kaleidoscope", which allows for the "Operation of Parallel Worlds."

Background
Zelretch's origins and details as to how he reached the Second Magic are unknown. He was responsible for the defeat of Brunestud of the Crimson Moon, the King of Vampires, in a fight many centuries ago simply because of his dislike for Brunestud. During the battle, Zelretch had his blood sucked, resulting in the Wizard Marshall being turned into a vampire classified as one of The Twenty-seven Dead Apostle Ancestors. While he emerged victorious, or it could possibly be said it ended in a draw, he paid a heavy price. He became extremely weakened because of the battle, aging him severely and causing his powers to diminish.

Despite his status as a vampire, Zeltretch still remains an ally of humanity and the nearly extinct race of True Ancestors. He was one of the Magicians who would be summoned to witness the births of princes and princesses like in ages past, and one such event was the coming of age ceremony of Arcueid Brunestud eight hundred years before Tsukihime. Along with his friend Caubac Alcatraz, they appeared before her and Zelretch, having "sent away" the King of the Moon, was very intrigued by her. He smiled and said "This is why life is interesting" upon seeing her. She also took an interest in him due to it being her first time seeing a smiling face.

He told her that she will sleep until she becomes an adult, and she asked him why he was smiling, because no one at the castle ever smiles. He said that people smile when they enjoy their own lives, which she did not understand due to her unique upbringing. When asked what is enjoyable and when she will understand, he replied that it was a fifty-fifty shot that she would come to that realization, and that due to her long life, she would have many opportunities. Understanding is something gained by chance, like walking alongside the road and tripping over a rock, and once something is understood, it is no longer anything special. She did not and could not understand, but he said to her that "One day you will notice that life is fun just being awake."

When visiting the Mage's Association, he is known to simply take pupils on a whim, but as his tutelage, while comprehensive, frequently traumatizes or cripples the most promising of students, there has yet to be a successor from any of his the family lines that follow his teachings. The idea of becoming “a pupil of Zelretch”, the "pupil of a Magician", is synonymous to being turned into a complete wreck, but those that are accepted as the "pupil of a magus" turn out to be fine. When he does appear, the department heads worry over having to send their most promising students in order to force him to leave, but at the same time worry that they will be unwilling or incapable of continuing their careers.

Nagato Tohsaka is considered to be one of the rare talented pupils that returned without a scratch, but the nature of their relationship was strange. Zelretch met him while both of them were on a journey, and he decided to teach Nagato something as payment for picking up the hotel bill. He couldn't even be called "pupil of a magus" because, from Zelretch's perspective, Nagato was only a follower whom he looked out for every now and then. Their level of relationship was distant, something like that of a supervising teacher who is observing the students doing experiments from afar.

Despite their strange relationship, Zelretch entrusted the design of the Jewel Sword to Nagato and the Tohsaka family. Though there were other candidates to whom he could have given them, such as the brilliant Einzberns and Makiris, they were fundamentally evil. Nagato, while mediocre, was good at heart, so he concluded that "this House will probably never accomplish anything great, but at least they will never stray from the righteous path." He then gave the design to Nagato and told him "alright, it will be a struggle, but work towards this goal". He never expected that only six generations would be needed to produce a result.

He helped oversee the formation of the Fuyuki Holy Grail War system two hundred years ago with Zouken Makiri, Justeaze Lizrich von Einzbern, and Nagato. Nagato allowed his property, Fuyuki City, to be used as the battleground, Zouken proposed the system of "Masters" and "Servants", and Justica developed the Heaven's Feel system, offered the homunculi vessels for the Grail, and became the core of the Great Grail.

Personality
Resembling Jotaro Kujo, he is known as a complicated and weird individual with a personality where he becomes angered with those who are evil and laughs at do-gooders. He has a demeanor that can be called "old, but not old."

He is surprisingly meddlesome in worldly affairs, and he is known to be a troublesome figure who frequently sparks conflicts. He acts as a surrogate grandfather to Arcueid Brunestud, and is both admired and disliked by the Mage's Association due to his tendency to cripple his proteges.

Heaven's Feel
Zelretch appears before Rin Tohsaka at the Clock Tower after she manages to recreate his Jeweled Sword with the assistance of Shirou Emiya during the Heaven's Feel route, complimenting her accomplishment by taking her as a protege and having the charges against her nullified. He had expected the least out of Nagato's unremarkable bloodline, ruminating on the progression of the Tohsaka family in just six generations.

Abilities
Zeltrch has complete mastery of the Second Magic, which allowed him to defeat Crimson Moon in one on one combat due to Crimson Moon having no knowledge of Magic, and allowed him to stop the "Moon Fall", during which Crimson Moon dropped a mirror image of the Moon towards earth, with pure force. The encounter caused a heavy toll to be taken on his body, known for his strong and tough physique, which aged him considerably and diminished his powers to the point where he can no longer use that level of magic extensively. After being bitten and becoming a Dead Apostle, he has gained limited immortality and he is recognized as one of the strongest Dead Apostle Ancestors. He mainly uses what is left of his abilities to travel between parallel worlds. Along with being a Magic user, he is also at the pinnacle of magi, earning his title as a Wizard Marshall. He has a number of Mystic Codes that utilize the Second Magic.

Jeweled Sword of Zelretch
Zelretch's main weapon is the Mystic Code, the Jewel Sword Kischur Zelretch Schweinorg (宝石剣キシュア・ゼルレッチ・シュバインオーグ), more commonly referred to as Jeweled Sword of Zelretch (宝石剣ゼルレッチ), the Jewel Sword (宝石剣), and Zelretch. It is a ritual dagger with a jeweled blade, an alien technology embodying general knowledge from a far future, beyond the reach of modern man. Shirou cannot tell the magical theory that constructed it even with all of Archer's knowledge. He carries the original, and he has left blueprints of the sword with the Tohsaka family as a sort of long-term homework that he expects will take many generations. Like normal Mystic Codes, it is only able to be used by him and those of his lineage. It is the tool with which he pushed back the mirror image of the moon by utilizing it to create a virtually limitless Ether Cannon unleashed through a Magic Square, a special magic circle.

The sword is capable of the Multi-Dimensional Refraction Phenomenon, allowing the user to draw in potentially infinite prana. The kaleidoscope-like jewel blade creates a small opening to the same area in another parallel world, though any further interference is impossible, and it draws in all of the prana from that space. Prana channeled into the blade can be fired off in a blinding stream of light. The capacity of the blade is limited, so the attack power will always be the same no matter how much prana is drawn. Also, as a jewel, the sword can also be detonated as a one-shot explosive. The sword is created during Heaven's Feel by using the blueprints, Emiya Shirou's Projection, and Illyasviel von Einzbern's inherited memories from Justica of Zelretch's original sword. The sword is inferior to the original, and using it causes Rin's muscles to be damaged. Due to this, Tohsaka Rin is better able to grasp the  blueprint and theory, generations ahead of when Zelretch expected, though it will take decades and numerous resources to reproduce it.

Other inventions
He is also the creator of the Kaleidostick, a sentient wand that hates its creator. The Kaleidostick, Ruby, is capable of forming a contract with its wielder, allowing it to use an ability known as Prism Trance to "download" and transfer knowledge from an alternate version of its user into its current wielder. It also provides an ample amount of prana, but it also likes to manipulates its wielder into humiliating situations. In Fate/hollow ataraxia, the Kaleidostick is responsible for transforming Rin into the magical girl Kaleido-Ruby, and a sister wand, Sapphire, is introduced in Fate/kaleid liner PRISMA☆ILLYA.

Rin uses Zelretch's Treasure Chest, an heirloom of the Tohsaka House, in hollow ataraxia, which looks a “genuine treasure chest” on the outside. It is actually a "magical chest" that spacial distortion inside of it made by applying the Second Magic. The dimensions fluctuate and bend according to the contents, allowing most items to fit into it, and one hour inside is equivalent to one day outside. She keeps the Kaleidostick and the Jewel Sword's blueprints in it. Also, while trapped in the chest, Shirou and Rin managed to call three years into a parallel world's future using a cellphone, having a confused discussion with that future's Luviagelita and Rin.

Neco-Arc is suggested by Aoko Aozaki to have been brought from another world by Zelretch in Melty Blood Act Cadenza.