Regulus Corneas (レグルス・コルニアス) was a Sin Archbishop of the Witch Cult, representing greed until he was defeated by Reinhard van Astrea, Natsuki Subaru and Emilia. He was one of the primary antagonists during the fifth arc of Re:Zero.
Regulus is a young man of medium height, with a not too thin yet not too muscular build and with naturally white hair that is neither too long nor too short nor is it arranged in any specific way; he's described as looking like a completely normal man. His face does not bear any notable features. He has gold eyes that do not particularly shine, except when he starts rambling about the things he deems important. There is a blue earring hanging from his right ear. He's usually seen wearing a white suit that perfectly matches his hair and a blue long-sleeved shirt of which, only the sleeve edges are visible. The suit itself is white on the outside and black on the inside, with the buttons and the sleeve edges being gold in color. Perhaps the most striking detail of his suit is the collar, which has an intricate, black and gold design. The suit is neither extravagant nor shabby. In the Web Novel version of Arc 4, Regulus is seen wearing completely black clothes.
During his wedding with Emilia in Arc 5, Regulus makes his appearance in a more formal wedding suit. He's wearing a white tuxedo with a long back that goes down almost to his heels, a blue and white striped shirt with a black and gold striped ribbon, white gloves and white shoes. The tuxedo's color pallet is the same as his normal suit.
Regulus was talkative, and tended to describe himself as "unselfish" despite representing greed. He would often go on and on about plausible theories, though in actuality he forced his own selfishness on others and tried to justify it. If his opponents had said something that went against his opinions and beliefs, he would find unreasonable faults in them, becoming angry while accusing them of "violating his rights".
He was extremely prideful and viewed himself as a "divine being" or "the most satisfying existence in the world", which greatly hindered his assessment of people, no matter if they were his enemies or allies, to the point he would make light of the Sword Saint, mocking him and calling him "a moniker of some guy who knows of nothing but swinging a sword". He often pointed out his dislike for needlessly involving himself with others. His hot-tempered personality often resulted in unneeded fights, however due to his overwhelmingly powerful Authority of Greed, he always came out victorious and unharmed. Due to his long life as a Sin Archbishop without ever getting his life threatened, he grew naive and arrogant; he disclosed his secret to Subaru, who in turn was able to connect all the dots and unravel his formidable Authority, allowing Reinhard to deal the finishing blow. In his final moments, Regulus revealed how he hated being looked down upon or laughed at, going even as far as saying he became a Sin Archbishop just so he could protect himself and his kingdom from such people; whoever offended him or his wives would end up getting killed, no matter their acquaintanceship with him. Regulus never realized his "sins", not even in the moments before his demise. His view on the world was corrupt and distorted from the beginning until the end.
More than 100 years ago, Regulus used to live with his family. His father was an alcoholic but tried to be a good father, his mother complained about bad earnings but apologized for it occasionally, and his two brothers who were sometimes mean to him but gave him their share of their meal if he accidentally spilled his. At some point in the past, Regulus obtained the Witch Factors of Greed, and subsequently killed his entire family, then village and then everyone in the surrounding cities. He broke his childhood love's mind, slaughtered her family and forced her to marry him, thus making her become his first of many wives.
He was also a Sin Archbishop of the Witch Cult 100 years in the past and participated in the attack of the elven village in Elior Forest along with Pandora. He had a one-sided battle with Petelgeuse Romanee-Conti who just took in the Witch Factors of Sloth, cutting both of his hands off in a relatively short time. Just before he was about to deal the finishing blow by smashing Petelgeuse's head open, Fortuna interrupted him, which greatly angered him. When Pandora calmly asked him to spare Petelgeuse's life, he lashed back at her and threw dirt at her, killing her instantly. Soon after, Pandora used her Authority of Vainglory to erase her death and proceeded to teleport Regulus back to his mansion, reverting the damage he has done to Petelgeuse and Elior Forest.
Fifteen years before Subaru's arrival, Regulus single-handedly took down a heavily fortified Vollachian city of Garkla, housing thousands of soldiers and the Vollachian hero Kurgan. Rumour has it that at the time, a Meteor supposedly belonging to one of the six Witches was located in the city itself (it is confirmed the Meteor did not belong to the Jealous Witch. It is not known if the Meteor was actually present or if it was only an excuse to drive the Witch Cult to take action.
Authority of Greed (強欲の権能 Gōyoku no Ken'nō): Regulus was able to use the Authority of Greed until his Witch Factors were taken by Natsuki Subaru following his death.
- Stillness of an Object's Time (物体の時間の静止 Buttai no Jikan no Seishi): The user can stop the time of themselves or anything they're wearing, touched, or even their breath. This stops any interference from outside and only allows the user's interference outwards. While this ability is active, the user cannot receive any sort of damage, no matter the power or destruction of the attack. The atmosphere released from the stillness can cause shock waves and it can enable the user to travel at extremely high speeds. Normally, multiple uses of this ability can be deadly as the user's own heart also stops, however it can be circumvented when combined with another of the Authority of Greed's abilities.
- Small objects imbued with Stillness of an Object's Time create devastating and destructive attacks. Regulus stops the time of pebbles, gravel or dirt and throws them at an enemy. These objects will travel through anything and anyone, resulting in the object or a person's destruction, as seen when he managed to hit Pandora and Subaru's left leg. He is also able to bombard a whole street with water droplets, destroying everything in its path.
- Apart from pebbles, dirt, gravel and other objects, he can also create an invisible wall of death by stopping time of his breath or stopping time of the air produced by his hand's movement, effectively creating an invisible blade of air that will cut everything in its path. His kicks are powerful enough to collapse entire buildings.
- Lion's Heart (獅子の心臓 Shishi no Shinzō) or Small King (小さな王 Chīsana Ō): The user merges their heart with one of the people of his kingdom, or in other words any woman that the user has confirmed to be their wife. With this, the user can use the effects of Stillness of an Object's Time as long as they wish to. As it is only a pseudo heart, even if the merge is destroyed the only aftereffect is that the user bears the burden again. Any conditions or effect area haven't been shown.
- As of a hundred years ago, Regulus had 78 wives, and as of Arc 5 he is mentioned to have had 291 wives in total. However, according to Sylphy, 238 of those wives were killed, leaving only 53 alive.
- Regulus originally intended to make Fortuna his 79th wife, but due to the unfortunate events that took place, he was unable to do so. 100 years later, he encountered Emilia, setting his mind on marrying her, making her serve as Fortuna's substitution.
- Regulus, from Latin, means "Little King".
- His namesake is a reference to the star Regulus, which is the brightest star in the Leo constellation.
- Regulus was mentioned to be a young man 100 years ago.
- To this day, he is the only person that managed to kill Reinhard.
- Regulus is the strongest Sin Archbishop of the Witch Cult.
- Regulus owns a mansion, however its location is unknown. In Ayamatsu IF Natsuki Subaru and Elsa Granhiert burn his mansion to the ground in order to get rid of his Authority and kill him.
- Despite him being the strongest Sin Archbishop of the Witch Cult, and killing Reinhard, he never managed to kill Subaru.
- The author stated that due to his overwhelmingly powerful Authority, if Subaru wasn't present in Arc 5, Reinhard would not be able to defeat him.
- According to the author, Regulus' Authority of Greed is the strongest combat ability in Re:Zero.