Al wears a black Vollachia made helmet along with a green vest, tan pants, sandals, and an orange cloak. He wears the helmet to hide the injuries on his face and also only has one hand due to an incident while he was in Vollachia. He carries his sword in a sheath on his back.
Al has a frivolous and goofy personality, and having spent more than ten years in a different world, he was easily able to get along with Subaru. Despite being Priscilla's knight, he doesn't really recognize himself as one, seeing himself as her caretaker, while Priscilla herself sees him as a handyman and a fool to entertain her. He has no qualms about their relationship. He also brags that the only way he can fight is by outwitting people and catching them by surprise.
Despite his easy going attitude, Al is deeply affected by having a form of amnesia. Until he met Subaru he sometimes had episodes where he would think of himself as losing the plot due to the memories he had from Earth. It's unknown how Al's amnesia came to be.
Al was summoned to the different world 18 years earlier. One time, he visited the Gladiator Island Ginunhive in the Vollachian Empire to learn how to fight and received a sword, however, he also lost his left arm around that time. He spent nearly 10 years there as a gladiator fighting in the Colosseum until one day one of the gaolers let him escape because they could see that his eyes were full of purpose, unlike the other gladiators. To help him fund his journey out of Vollachia the gaoler gifted him his trademark black helmet which was made in the image of the helmet worn by one of the Colosseum's heroes.
Sometime later, Al joined Priscilla's knight tournament an event with around fifty people participating, but failed to win. However Priscilla decided to choose him as her knight instead of the top 4 contestants.
Al is apparently acquainted with a Sin Archbishop, as he told Capella that she was "considerably different from the Sin he knew". He also is in some way acquainted with the Witch Cult and the Witches of Sin, as he knew that Typhon died in Priestella, where her remains resided, and he also knew about Gluttony's authority.
Unknown Ability: Al has some sort of ability which allows him to repeat a certain amount of time over and over again with other people being oblivious to its effects, though sometimes his opponent can tell if he's returned, and he himself refers to it as a bet. He used this ability to evade and/or test Capella's blood multiple times to make sure he wouldn't get infected just by stepping in it and she noted that she didn't see him evading it at all. Al can only negate his or others' injuries or deaths while his ability is active, in addition to only working within a limited area, which he refers to as his territory. In one instance where he used his ability, it was described as twisting and wrenching of the space around him as it activated and filled the area up. The effect was likened to the kind of imbalance you'd see from looking at the world reflected through a bubble on the surface of some water, or from receiving an intervention from a supernatural being.
Magic User: Al is able to use Earth Magic.
- Dona (ドーナ): The user summons one earth wall, which is used as a defensive spell.
- El Dona (エル・ドーナ): The user conjures a swarm of earth mana and pinpoints it at the body of a target, usually channeled through a medium, which then the effected area bursts into spikes from the inside out and expands outward.
Equipment: Al owns a weapon called the Blue Dragon Sword and wears a black helmet which he received when he was at the Gladiator Island Ginunhive. Priscilla asked him one time if the helmet was a replica of a helmet related to the Gladiator King and he confirmed it.
- According to the author, Al is involved with one of the three mysteries of Re:Zero, and revealing his circumstances would answer it.
- Also, Al is scheduled to be featured in Arc 7.
- Al's full name Aldebaran is the brightest star in the Taurus constellation.