Skrael and Bellroc share a cordial relationship, with Skrael being more subservient and polite towards them. Bellroc seems to be the more influential of the two. Their relationship, however, goes no further than partnership, as Bellroc didn't show the slightest concern when Skrael died and did berate him for torturing Steve, though this was because Skrael was interrupting her.
Bellroc used to be on good terms with Nari. After she defected from the Arcane Order, Bellroc became more cold and hostile towards her, showing no reaction when Skrael immobilized their sister with ice while kidnapping her. They did show some slight concern when Douxie claimed that "Nari" (really Archie in disguise) was ill.
After King Arthur was resurrected by them, Bellroc and Skrael made him accept their ideals and took him on as something of a servant. Arthur was very subservient towards Bellroc, viewing them as his master.
Initially, Bellroc and their siblings resurrected Morgana and gifted her the title "Eldritch Queen" as a gift for her service to magics. In reality, Bellroc merely saw Morgana as a pawn in destroying humanity and taking over the magical world. When the witch realizes the error of her ways, she turns against the Order to help the Guardians of Arcadia defeat them.
Bellroc views Douxie as a foolish child and hates him for being Merlin's apprentice, as well as fighting against them and the Order. After the death of Merlin, Douxie took Merlin's place as their mortal enemy.
Bellroc and Jim clearly see each other as enemies.
In Wizards, Bellroc used King Arthur to possess him, and used him as a mere pawn. Bellroc also was willing to use Jim as a bargaining tool, and even reffered to him as a "troll mongrel".
In Rise of the Titans, Bellroc acts ruthless towards Jim, toying with him when he tries to fight them head on, and sadistically taunts at how powerless he truly is without his amulet, believing him to be a frightened little boy. They even show no qualms tossing him off a subway train and leaving him critically injured. Bellroc also taunted him about how he had no armor or amulet, and still considered himself as a hero. Despite offering him a chance to spend his final moments with his loved ones, this wasn't genuine compassion and was rather a taunt to make him give up hope. It is also implied that Bellroc was going to kill him anyway, as Jim wouldn't resist. After this, Bellroc made multiple attempts on Jim's life, and even stabbed him with a shard of her staff. Bellroc, was ultimately slayed by Jim.
Like other members of the Arcane Order, Bellroc hates Merlin because he was the one who stood up against the destructive actions of the Order and hid the Genesis Seals from them. They also view Merlin as a cut-price imitation of a wizard who is not fit to hold that title.
Bellroc views Claire as their and the Order's enemies, given she fights against the Order's ideals and has stopped them from capturing Nari on multiple occasions.
Bellroc views Steve as one of their enemies, seeing him as an incompetent buffoon.
Although the two only confront each other briefly during the Battle of Killahead, Bellroc saw Deya as a "mundane, simple creature that stains magic" (despite the fact that Deya is a troll, a type of magical creature). When they try to engage the first Trollhunter in battle, they end up getting themselves permanently blinded by the Sword of Daylight.