Ben was Tim's mentor when he was still training to be a monster slayer. He's a no-nonsense veteran, who's seen and done a lot. He used to admire Tim's dedication, but thanks to the Elders' lies, he now believes that Tim is a monster who managed to deceive everyone. His team is currently trying to track down Tim to bring him back to the Order's secret Headquarters - dead or alive. They got close in the end of Mummy Issues, where Ben showed he wouldn't hesitate in killing his former apprentice.
Nikki is Ben's daughter and had wanted to become a monster slayer since she was a little girl. However, her father refused to let her join because he felt it was too dangerous. She had been planning to apply to the Order in secret when she was kidnapped by Krampus (Tim's Winter Adventure). Her helplessness made her feel like her father had been right all along, but after realizing that even if she led a normal life she'd always be in danger, Ben changed his mind. Nikki is currently an Order recruit and part of her father's monster slaying team, but she has doubts about Tim's guilt.