Marin is a lawyer who lives on the outskirts of Crescent Lake with her long term romantic partner Marisa, and works in town as well as surrounding areas for cases. She put herself through law school, but unforeseen circumstances led to her petitioning for the bite from Sara Ross after graduation. She owes Sara her life, and is thus extremely loyal to her alpha and the pack.
Marin Grundy is a thirty-one year old werewolf. She is nearly six feet tall with pale skin, long blond hair, and blue eyes. She has a trim, athletic body that she's comfortable with showing off.
As a werewolf, Marin has thick fluffy fur the same color as her hair. Marin is stronger than other werewolves, but not as fast or agile. Marin's strength and stamina makes her a strong fighter with a scrappy fighting style. She is able to pick up other werewolves with apparent ease.
Marin is a kind and loyal person as well as a put-together and competent adult. After helping to raise many of her siblings, Marin is familiar with the role of a caretaker. When training Malaya she did her best to encourage the younger werewolf and helped take care of Elias when he was covered in wolfsbane. She also helps to teach Ginger spelling.
Sara Ross saved her life by turning her into a werewolf and Marin is extremely loyal to her and the Ross Pack because of this. She uses her werewolf abilities and her skill as a lawyer to assist her pack and her friends.
Marin was raised in a conservative Christian family and has a large number of siblings who she helped raise. When Marin was a teenager her parents continually attempted to set her up with boys from their church. Her parents agreed to let Marin attend college with the conditions that she attend a conservative school and major in Religion.
While attending school, Marin discovered her attraction to women. Since she had no context for her attraction she discussed her attraction with a school counselor, who informed her parents. They disowned Marin. She finished the semester and then transferred to a state school where she got a full ride and began studying Law. She graduated with high honors, and entered into a Law program.
Struggling with Cancer
A year away from finishing Law school, Marin was diagnosed with a brain tumor. During her time in the hospital she met Marisa Salcedo, who works there as a nurse. When Marin's vision became too blurry to read, Marisa would read the newspaper to her and keep her company. When Marin's health continued to decline, Marisa introduced her to Sara Ross, who offered to turn Marin into a werewolf to save her life. Marin agreed.
After being turned, Marin made a fast recovery. She was discharged from the hospital and joined the Ross Pack. When she graduated from law school, many members of the Ross Pack along with Marisa were there to cheer her on. Not long after graduating, Marin and Marisa began a relationship.
- Marin's last name Grundy was chosen because she needed a last name she kind of hated, so she has one last thing to finally shed. Marisa made reference to Solomon Grundy when discussing about how her last name sounded like a "super villain name."
- Marin is a generous tipper 
- Marin is left handed. 
- In an interview, Shawn mentions that Marin, along with Malaya, are her favorite characters. 
- MarMar is Marin and Marisa's ship name. 
- Shawn has created a spotify playlist for How to be a Werewolf. Marin and Marisa have their own section in the playlist.
- In an early comic that started the idea for How to be a Werewolf, it is mentioned that the two featured characters were a proto-Elias and a proto-Marin. 
- Marin has Marisa listed as "Marisa <3" in her contacts list 
- Chapter 8 Page 374
- Chapter 8 Page 351
- Chapter 9 Page 455
- Chapter 7 Page 259
- Chapter 7 Page 261
- Chapter 7 Page 257
- Chapter 7 Page 266
- Chapter 7 Page 272
- Chapter 7 Page 274
- Chapter 5 Page 94
- Chapter 7 Page 268
- How to Be A Werewolf: Interview with Shawn Lenore, Clark, Lucian, July 25, 2017, Retrieved August 15, 2021
- Chapter 2 Page 32
- Chapter 9 Don't Ruin Your Boots
- Chapter 9 Page 462