Reid Astrea (レイド・アストレア) was the first Sword Saint and a key figure in the sealing of the Witch of Envy 400 years ago. Mentioned throughout the series, he formally debuted in Arc 6 as a secondary antagonist.
Throughout Arc 6, his soul acted as the overseer of the second trial of the Pleiades Watchtower and was a major obstacle preventing Subaru and his companions from conquering it, particularly toward Julius. He later achieved rebirth by taking over Roy Alphard's body, but the latter proved to be an unsuitable vessel and his soul shattered during his final duel with Julius, thus marking the end of the First Sword Saint.
Reid had waist length, fiery red hair, sky blue eyes, and was mentioned to be a head taller than Subaru with a muscular body. He wore a crimson kimono which he only wore half of, leaving the right side uncovered, a white sarashi around his body, and a black eye patch over his left eye that has an ugly pattern.
Reid was shown to have a very frank and rather crude personality, as Subaru was easily able to imitate his method of speech, and tended to speak in short sentences, frequently ending them with you (オメエ omee). However, he had no interest in titles, stating that he was himself, and others were themselves. He was also lustful, mentioning that he would've had Emilia in bed if he was still alive.
Despite being somewhat frank and abstract, Reid was quite clever. He seemingly knew about the powers of the Authorities to some extent, as he named himself Hauroy Rallior (ハウロイ・ラリオル) when he faced Lye Batenkaitos in Arc 6. In addition to this, he also had a great amount of knowledge regarding how to fight with the sword. Because of this, he had gained the alias as the "Heavenly Sword".
In Re:Zero Prequel: Loving the Days Gone By, it was revealed that Reid did not discriminate against who he pointed the tip of his sword at. Be it a spirit, a Demon Beast or a Dragon, Reid cut them down one by one. He only spared humans. Due to his campaigns against the dragons in particular, some of them have retaliated and decided to avenge their fallen brethren, however, to no avail as they were either cut down by Reid himself or by other powerful individuals of that era.
Reid Astrea was born around 400 years ago. Throughout the years, he trained relentlessly and soon achieved the very zenith of swordsmanship, being awarded the title of the Heavenly Sword.
In the years predating the Great Calamity, Reid accomplished a lot of things, meeting people such as the members of the Witches of Sin, the Divine Dragon Volcanica, the Sage Flugel, naming just a few. He also marked himself down in history for being the one responsible for the eradication of the Evil Dragons which used to roam the new world back then. According to legends, he cut down numerous dragons with a single swing of his Dragon Sword. After Satella, the Witch of Envy, suddenly went out of control and went on a rampage across the world, Reid met with Volcanica, Flugel and Shaula in the Kingdom's city of Flanders, forming an alliance with the heroes. The four heroes set their goals on defeating the rampaging Witch who mercilessly killed thousands and thousands of innocents and toppled one country after another. After realizing they were unable to kill her, Reid and the rest managed to defeat her and seal her away in the Sand Dunes at the very East of Dragon Kingdom of Lugnica.
It is not known what Reid did after the Great Calamity but after an unspecified amount of time, the first Sword Saint succumbed to old age and died peacefully.
Superhuman Strength: Reid was able to hold up a block of ice so massive that it covered the entire ceiling of the Pleiades Watchtower's second floor, Electra.
Martial arts: Reid was capable of a technique where he channelled the full power of his opponents' attacks harmlessly out of his body. It is hinted at that he could channel it out of any part of his body but had only done it through his feet. This technique effectively made him immune to attacks from clubs, hammers, punches, kicks or anything blunt.
Excellent Intuition: Reid could use his intuition to decide if he should cut something, including invisible abilities, like Subaru's Cor Leonis.
Master Swordsman: Reid was known for having peak sword-mastery and the martial arts of his time. As a testament to his peerless skill Reid was called the "Heavenly Sword". To this day, he is the most powerful swordsmen that have ever lived as he reached the zenith of swordsmanship, being able to cut beings, objects, concepts and magic alike. He was even able to cut Subaru's Authority of Greed and Beatrice's Ul Shamak with mere chopsticks. His sheer sword skill is said to surpass even that of the current generation's Sword Saint Reinhard van Astrea who's stated to be the most powerful character in the series.
- An unnamed sword strike: Reid unleashes a torrential wave of light that engulfs anyone and anything caught in its line of fire, blowing them away. It can cut light, the atmosphere, space and even dimensions and concepts; it is the ultimate goal of sword skill. Despite being a sword strike, Reid is capable of performing this attack even with a pair of ordinary wooden chopsticks. Unlike in Reinhard's case, when Reid performs this technique it does not result in the destruction of the weapon he uses. While strong individuals like Julius have been able to survive this attack, it is generally capable of vaporizing human beings.
- Vertical sword slash: During his final fight with Julius Juukulius, Reid finally decided to fight seriously and used an actual sword, rather than his chopsticks. By repeating a normal vertical sword slash, Reid unleashed a destructive torrential wave of light, scorching everything in its path. The attack was noted to be beyond understanding; a true testament of the first Sword Saint.
- Dragon Sword Reid (龍剣レイド Ryuuken Reido): Four centuries ago years ago, Reid received a special sword which was quickly named Dragon Sword after Reid often went on rampages with it, killing numerous dragons with a single swing. The sword is said to be unbreakable and is supposedly able to cut through any material, no matter the toughness or density. According to some legends, the sword even brought the Witch's end. After Reid's death, the Sword was given to his offspring who inherited the Divine Protection of the Sword Saint. As a tribute to the achievements Reid had achieved with this legendary weapon, the Sword inherited his name.
- A pair of chopsticks: In Arc 6, Reid can be seen with a pair of chopsticks. In his hands, the chopsticks are extremely durable and are able to withstand repeated sword slashes without chipping or breaking despite being made of ordinary wood. Reid even cut Subaru's Authority of Greed with them.
Inhuman Power: As a former Sword Saint and a key figure in the sealing of Satella, Reid had considerable strength, falling behind only Reinhard. He was easily able to defeat Julius and the Artificial Spirit Echidna and would've defeated Emilia if he didn't let his guard down due to his lust. Combined with his prideful and arrogant personality, he was able to overwrite Roy Alphard's Authority of Gluttony, effectively hijacking his body and achieving complete rebirth 400 years after his death; although in his fight against Julius his body began to "crack" because Roy's body couldn't contain Reid's soul. The author has stated Reid Astrea would easily be able to behead Regulus Corneas, Sekhmet, Beast of the End and Ram with her horn if he was to fight against them.
- Despite being a former Sword Saint, Reid didn't have the Divine Protection of the Sword Saint.
- His eyepatch is purely decorative. Both of Reid's eyes are in perfect condition.
- After Reid, every member of the Astrea family was born with fiery red hair.
- When asked who is stronger between Reinhard and Reid the author stated that it depends on the conditions, though Reinhard is mostly stronger.
- The author once mentioned there's a very high chance Reinhard would not be able to draw the Dragon Sword if he ever was to face off against the first generation's Sword Saint.
- 400 years ago Reid had an apprentice who he says had a very similar personality to Julius Juukulius.
- There is a book called The Legend of Reid Astrea about Reid's deeds, it was supposedly written by someone who was very familiar with him. The contents of the book are so incredible it's considered more fiction than fact.
- While not outright confirmed, it's heavily implied that Toska is a member of House Astrea and Reid Astrea's younger brother. Just like his supposed older brother, Tosca had flaming red hair and was inhumanly strong, though not nearly as strong as Reid.
- Reid was acquainted with a former Emperor from the Sacred Empire of Vollachia.
- "Well then, I'm the swordsman, Hauroy Rallior" Arc 6: Chapter 65. Section 1.
- "Gain his permission, by hand of the Fool who has reached the Heavenly Sword." Arc 6: Chapter 25. Section 2.
- "According to legend, Flanders is also where the Holy Dragon Volcanica was bound in friendship to the first Sword Saint Reid, and the Sage Shaura" Re:Zero Ex Light Novel Volume 3. The Silver Flower Dance of Pictat. Section 5.
- "You let all Miss Ram's attacks escape onto the floor with the bottom of your feet, huh." Arc 6: Chapter 69. Section 1.
- "A~h, so it finally got cut aye. You, don't be doin borin' shit." Arc 6: Chapter 69. Section 1.
- "Appearances, appearances, appearances... yeah, appearances aye. You really do be speakin' shit like my follower." Arc 6: Chapter 85. Section 1