* Frisk is main protagonist of Undertale. After Frisk falls into the Underground, they embark on a journey to return to the surface. Frisk is the last of the eight humans to fall into the Underground after traveling to Mt. Ebott.
* The story starts when Frisk is about to open the Door that keeps the Monsters on the Underground. With the help of Asriel and the six humans souls, they managed to break the Barrier, the magic seal wall that was closing the East Door. Unfortunately, despite being unlocked, the Door refuses to open. Frisk takes upon themselves to find out why.
* As a human, Frisk has a lot of determination. Their soul is red, the most powerful kind of soul. Thanks to that, Frisk is able to save or reset their time in the Underground. Even though, they end up being the only one remembering their previous actions. Or think they are.
* Frisk is aware of only one other person in the Underground with the same type of power than them: Flowey, the soulless flower, vessel of Asriel's spirit.
* Along their journey, Frisk has made many friend in the Underground as Sans, Papyrus, Undyne and Alphys. Toriel, the former queen of the Kingdom, ex-wife of Asgore and mother of the late Asriel and Chara, holds a special place in their heart as they see her as a mother. The two will eventually become a family.
* Flowey is a more complicated case, as they wish to be friend with him. But the flower's inability to feel emotions and resentment toward his actual situation make the relationship difficult. Thankfully Asriel's spirit sometimes helps to smooth things up.
* Frisk is a very kind soul and wish peace for everyone. Normally quiet and calm, they seems not used to express their feelings. They often keep their tough for themselves, worried it would bother their surroundings, making him holding a lot of secrets and untold stories.