Maddox is first introduced working with Isobel Flemming in a diabolical plan to capture Katherine Pierce, Alaric Saltzman, and the Moonstone. After kidnapping both, Alaric and Katherine, Maddox later advises Isobel that she was no longer needed, causing Isobel to die by exposing herself to sunlight. Maddox also casts a spell that caused the spirit of Klaus to possess Alaric. He later advises Klaus how to kill Bonnie and performs a spell that would protect Klaus from Bonnie's powers.
With the help of another witch named Greta Martin, together Maddox and Greta enchanted a spell that returned Klaus' spirit from Alaric's body, back into his own. Later, both Maddox and Greta were assigned in capturing Caroline, Tyler, and Jules. However, while guarding the prisoners inside the tomb, Maddox and Damon became involved in a violent confrontation, and Maddox was later shot by Matt Donovan, then dying of a broken neck caused by Damon.
Maddox was a young man in his 20s, with dark hair and a pale face, with an almost always stern expression. He always dressed in a preppy manner, frequently wearing a black coat.
Maddox, like Greta, was a witch who was extremely loyal to Klaus. He would use his magic to aid in Klaus whenever asked, such as the spell that transferred Klaus into Alaric Saltzman's body as well as putting a spell on him while in Alaric's body that would help protect him from most physical harm. If Klaus demanded it, Maddox would deliberately hurt or kill innocents, demonstrated when he attacked Alaric and Carol Lockwood.
Maddox is of Welsh origin, and the meaning is "Good; generous"
- Maddox is a Welsh name, meaning "son of Madoc". It gained popularity when Angelina Jolie adopted a baby with this name in 2003. It is the pen name of writer George Ouzounian, who got internet fame with The Best Page in the Universe.
- "My character is a guy named Maddox, and he's a warlock. It's kind of fun, because I basically hold up my hand and people go flying off walls."-Gino Anthony Pesi about his character. 
- Maddox was the first Caucasian warlock to appear in the TV series.
- Maddox served as Klaus' right hand prior to Klaus acquiring Stefan and then his hybrids.
- Since he worked personally with Klaus we can assume he is a very powerful warlock.