Born to a tribe connected to the old dragon legends of Unova, who currently reside in Lacunosa Town after being chased out of the chasm area in olden times. He was born with noted psychic powers, which is why he was given a forehead markings at a young age. He was kidnapped by Ghetsis in order to help bring about a prophesied legend so Ghetsis could become king.
Ghetsis was looking for the child he had conceived but the mother ran away, and Makaza was born in the expected time period, along with having psychic powers... Ghetsis assumed he had to be the right one, as N was the same. He renamed him to Black and had him work under N, while Ghetsis also worked to try and find a way to use Black's specific psychic powers to his advantage.
While Ghetsis (and N) would know about Black's abilities and taken preventative mental measures against it, being able to know the internal reasons the various Plasma grunts and admins were there prevented Black from being able to be brainwashed into supporting the group. He did genuinely care for and support N though, and eventually tried to convince N to run away with him, which only confused and angered N, leaving Black to run away alone as a teenager.
As he grew up, he worried about the injured, disabled, and bad temperament Pokémon that were taken in by Plasma but never really cared for as much. So, on the way out, he grabbed some Pokémon he knew were considered useless by Plasma standards, and would've probably been abandoned or killed. An Oshawott that can't develop a shell (which leads to it being unable to evolve as well) ends up being his main partner Pokémon.
He's been able to live on his own through various means thanks to his abilities. As of BW, he still hasn't tried seeking out his family as he's still unsure if he's either related to Ghetsis, or abandoned by his parents, and does not want to deal with the emotions that surround that. He still avoids battling and anything relating to the topic of Plasma.
Through a mixup (that is his own fault), Verity ends up with his Liberty ticket and catches Victini. He confronts her, claims she stole his ticket, and that he deserves to have Victini in return. The situation eventually cools down, but he remains a rival to Verity, and eventually Cheren and Bianca. They all feel iffy about him. Eventually, the group runs into N while Hilbert is with them, and N exposes that Hilbert's part of Plasma and his entire team is stolen as well. The others do not take well to this.
His main part of the plot is trying to be a mediator between N and Verity's strong beliefs and dislike of each other, making both upset at him. Of course, they eventually fly off on their dragons, leaving him behind. He ends up getting unwillingly involved with Neo-Plasma in B2W2 in some capacity, which leads to his involvement with Kyurem.
The maiden of legend, named Mzatan, though the name's been lost to time. Worked as a trader as a child and teen, so was able to communicate proficiently with the colonialists. Her psychic powers, communication, and presumably family lineage allowed her to become a chief as a young adult. This mostly entailed trying to keep relations between the groups decent while protecting their own interests... until the dragon is somehow split and war looms on the horizon. After getting constantly caught in drama between the two princes, she sets out to find the missing third dragon in the chasm, and never returns. Soon after this, war fully breaks out and the region is fully brought into the kingdom's control... leading to legends and beliefs that the dragon killed the maiden and essentially cursed the area, leading to the fear and hatred of Kyurem.
(Kyurem denies these claims, and points out that humans in the 1700s tended to drop dead of almost anything in frigid open chasms).
Travels alongside N, who is a veterinarian of sorts. Both of them escaped from a cult and travel the area together, a bit lost.
A windigo. In such a universe, windigo can either be natural incarnations of winter, or humans who performed actions that allowed them to turn into one. The latter are generally much more violent, though people often assume it's the former that are the problems (people, naturally, have more mercy and forgiveness for those they feel they can relate to, and humans are closer to most people...). Hilbie is a natural incarnation who works under Kyurem, an infamous creature who probably has a mix of truths and falsehoods to his bad reputation.
Hilbie is relatively young, and since Kyurem spends so much time sleeping, he ends up spending a lot of time hanging out at various other places... and LARPing as a ningen. After troubles start up with the dragon clan, Kyurem tells Hilbie to figure out the situation, as Kyu has existing very bad blood with them. Hilbie falls back onto the excuse of being a human who was forced to work for Kyurem in order to keep him happy, after he's sussed out as being connected to him. Naturally, he ends up getting a bit close to Hilda and N. And he will be mocked when exposed.
He probably has multiple different names, a lot of non-humans love having nicknames for identity hiding reasons. His real name is probably long and based on Mza, since it means ice. Makaza, Black, Hilbie, are probably all nicknames he's had. Also, the main non-human traits that show are the antlers (which can be hidden) and the coldness (which is probably worse than vampires... but wearing heavy winter clothes constantly at least makes it not noticeable to others).
Is more successfully brainwashed by Plasma, so helps their cause. After Plasma wins, Black works as an interrogator, and has a horrible reputation by anti-Plasma groups. No one knows much about him except that he is able to perfectly get information out of people, which leads to rumours he's some ex-FBI torturer or something like that... (of course, he's just asking questions, listening to what they think, and going off of that instead of anything they actually say). He always wears the trademark Plasma cloak, so people can't see how young he is, but do know him from his forehead mark. (Ghetsis says it's best he shows it off as it intimidates people, which Black doesn't like hearing.)
He still is generally uncomfortable with how Plasma runs things, but at this point feels he has no options, being so deep into the organization. Sometimes he runs off to just be by himself for a bit in the forest to get his mind off things... and that's how he ends up finding the commune Verity is at by accident, and deciding to stick around for a second to try and listen in... and is so distracted by that, that he doesn't notice the physical sounds of being approached. And so, he is captured by the commune and held for information.