Hazel was a member of Salem's group, having chosen to join her after Gretchen's death. However he did not get along with his colleagues, being either indifferent or even sometimes antagonistic with Salem's other lieutenants. In "Witch", he defected from her side after learning about her true goal, and later sacrificed his life to delay her.
Hazel was Gretchen's older brother. Hazel cared deeply for his sister and her death at Beacon Academy was his original reason for wanting Ozpin dead. When she was alive, Hazel was against her joining Beacon to become a Huntress. Gretchen's death had a profound impact on her brother, leaving him a broken and vengeful man who was clearly still grieving despite the untold number of years since her passing. However, after his conversations with Oscar in Monstra, and realizing that he was telling the truth about Salem, Hazel chose to do what he believed "Gretchen would have done" and helped Oscar escape.
Salem's Inner Circle
Initially, Hazel tried to kill Salem when she sought him out, but upon realizing and seeing first hand of her immortality, Hazel gave in and became a member of her group instead. He claimed to Ozpin that he and Salem shared the same vision of no Kingdoms and Huntsman Academies, most likely because he didn't want anyone to go through what he went through when he lost his sister.
Despite following her orders, he was deeply afraid of her and greatly feared her wrath. After their loss at Haven, he unintentionally incured Salem's ire when he attempted to take responsibility for the defeat and risked her anger again when he interrupted her with further news. As he saw Grimm hands rising around his feet, he reported that Ozpin was taking the Relic of Knowledge to Atlas, and quickly vacated when Salem ordered him to depart. In "Our Way", as Salem created an army of winged Beringels, Hazel admited to Mercury Black and Emerald Sustrai that their master was taking matters into her own hands.
In "War", Ozpin revealed that Salem was only using his anger to manipulate him, stating that her only goal was the destruction of Remnant in order to die. This would ultimately make Oscar share the password for the Relic of Knowledge, hoping he would see the truth for himself.
In "Witch", after confirming the truth from Oscar, he turned against Salem, helping Oscar and Emerald escape from Monstra. When Salem asks him if he gave up vengeance after so many years, he replied that he was doing what Gretchen would have done, and goes to fight her, buying them time to escape. Knowing he would not survive the battle, Hazel deliberately overdosed on Dust before fighting Salem.
His only acknowledgment of Cinder was to speak ill of Cinder being thwarted by Ruby Rose, though in doing so he also acknowledged her as a peer. Although the two worked together at Haven, he showed no outward reaction to her defeat. Regardless, when being questioned by Salem, Hazel still attempted to take responsibility for Cinder's failure to no avail.
Cinder in turn was shown to possess a level of respect and faith in Hazel's abilities and skill, this was seen where Cinder stated that she was confident that Hazel was strong enough to fight and kill a fully trained Huntsmen.
The two had no significant interactions but Hazel didn't seem to get along with the disgraced doctor. This was shown when he gave Watts an unimpressed look while he mocked Cinder for not being able to talk after her defeat by Ruby.
Hazel and Tyrian appeared to have a unfriendly if not outright hostile relationship. Given how the scorpion Faunus sadistically mocked him, Emerald, and Mercury for their defeat at Haven Academy to which Hazel reacted with a glare and told the two to ignore him.
Hazel fought alongside Mercury and Emerald during the Battle of Haven. But after they seemingly lost Cinder and the Relic of Knowledge, the three of them were forced to retreat. Hazel carried an unconscious Emerald after she overtaxes herself from using her Semblance.
When they returned to Salem's palace, he told them to ignore Tyrian and proceeded inside. When Salem asked who was responsible for their defeat, Hazel initially took the blame on himself in order to deflect it away from Emerald and Mercury. Later, when Salem ordered everyone to clear the council chamber, Hazel urged Emerald to comply and led her outside. In "Our Way", as Mercury and Emerald watched Salem create a new Grimm army, Hazel explained that she intended to do battle herself.
In "War", both Emerald and Mercury were shown to have a strong sense of respect for Hazel. This was seen when Mercury stated that he was a example that he and Emerald should follow in regards to their affiliation to Salem.
As seen in "Witch", Hazel genuinely cared about Emerald. After realizing that Oscar was telling the truth, Hazel made it clear he planned to have both Oscar and Emerald escape Monstra together.
Later when Emerald was about to be interrogated by Salem due to believing she had something to do about the Lamp's disappearance, Hazel saved her by punching Salem away from her, releasing her binding. Upon Hazel making it clear he planned to fight Salem despite being out classed, Emerald weakly tried to convince him to escape with her. Touched by this gesture, Hazel nonetheless told her to escape while he kept Salem busy, bidding her farewell.
Ozpin informed Oscar in "Kuroyuri" that Hazel was someone from his past and advised Oscar to be wary of him as a result. In "Vault of the Spring Maiden", the reason why he wanted Ozpin dead was because he blamed him for his younger sister's death. His vendetta against Ozpin was originally of such magnitude that he felt the need to kill him in every incarnation that he could possibly get his hands on, determined to make him suffer over and over again.
When they met again after Hazel tortured Oscar for information on the Relics, Hazel was shown to be furious with Ozpin for letting Oscar take the beating instead of him. While Ozpin told Hazel the truth regarding Salem's true plans in an attempt to get him to turn on her, Hazel originally didn't believe him until he told him the password to the Relic of Knowledge was Jinn so he could learn the truth for himself.
When Oscar had trouble getting a train ticket out of a machine at a train depot due to lack of funds, Hazel showed up and banged on the machine. This caused a train ticket to fall out of the slot. Before moving on, Hazel advised Oscar not to let such a small obstacle obstruct his path.
When they met again in Haven Academy, Hazel was shocked to learn that Oscar was the new incarnation of Ozpin. Though he attacked him, he said his blood would be on Ozpin's hands, and he hoped Oscar could forgive him for seeking to kill him.
In "Fault", Salem tasked Hazel with torturing Oscar for information on the Lamp. Though Hazel went through with it, Oscar could tell that Hazel wasn't going all-out in torturing him as he saw Oscar as just a kid and indeed Hazel tried to convince Oscar to just surrender, promising to stop torturing him. He expressed disgust at Ozpin when he finally emerged for not taking the torture himself and letting Oscar suffer.
In "War", Hazel was at first suspicious when Oscar told him the password to the Lamp, but when he realized that Oscar was telling him this so he use it himself, made him uneasy. Eventually, due to seeing how honest and straightforward Oscar was when telling him, he managed to get through to Hazel as he started to believe him.
In "Witch", Hazel allowed Oscar a chance to prove himself by activating the Lamp and when he proved the sincerity of his claims, he decided to turn against Salem and help both Oscar and Emerald escape. He even fought against Salem directly when asked to take Oscar back to his cell. Hazel later gave Oscar an opening against Salem and told him to attack both of them without hesitation, even if the attack would also kill him.
Despite being assigned to work together by Salem, Hazel and Adam had little to no respect for one another. The pair were seen meeting with Sienna Khan in "Dread in the Air", to gain her loyalty to Salem's Faction. However, Adam enacted a coup and overthrew Sienna as High Leader, a plan Hazel knew nothing about. Hazel was upset with Adam keeping secrets from him, along with killing Sienna when he deemed it unnecessary.
The lack of cooperation between them was shown again in "Downfall", when Hazel refused to help Adam after he and his forces were confronted by the Belladonna's, armed citizens of Menagerie and the Mistral Police. It's unknown if Hazel knew or even cared that Adam died.
Wanting to obtain the White Fang's support and loyalty, Salem ordered Hazel to negotiate with Sienna, in order to recruit her to their cause.
In "Dread in the Air", Sienna showed active distrust and hostility towards Hazel and made it clear that neither Hazel nor Adam knew what she truly "wanted" and threatened him to leave under the threat of death.
After Adam killed her and usurped control of the White Fang, Hazel was shown to be saddened by her death.
Hazel went to Lil' Miss Malachite in order to inquire information on Ruby and her group after their failure in destroying Haven Academy and obtaining the Relic of Knowledge.
In "So That's How It Is", Hazel gave this information to Salem.
- RWBY Volume 8 Directors' and Writers' Commentary Chapter 9
- RWBY Volume 8 Directors' and Writers' Commentary Chapter 7