WARNING!!! PAGE MAY CONTAIN SPOILERS FOR THE GAME "UNDERTALE"!!! READ AT YOUR OWN RISK!!!
Frisk is the playable character of Undertale, who attempts to escape the Underground and go back up to the Surface. They are the last of the eight humans to fall into the Underground after traveling to Mount Ebott.
They are not the fallen human the player names at the beginning of the game. Their name is revealed only during the ending of the True Pacifist Route.