Frisk is the main playable character of Undertale. He looks like a child of dubious gender. The player will find out that he is called Frisk only in the process of passing the Pacific route. He is one of the eight children who appeared in the Underworld universe falling down from the Ebott mountain. In the game, you will lead him through the lands and make him come back home. During his adventure, he communicates with other characters, but when the player has nothing to say, the dialogue won’t appear. During the battles, the window in the center of the screen will show the words he said during the previous dialogues.
Depending on the ending you are approaching to, other characters will treat Frisk differently. In case you follow the Pacific route, demons claim him to be kind and carrying. In case you choose the Genocide one, they will call him gloomy and evil. Flowey and Sans will perceive the protagonist as something inhumane because he is guilty in numerous deaths and terror. There is an opinion that Chara possesses Frisk’s soul when the route of Genocide is chosen. Reloads and savings will change his memory, that is why some characters will notice that Frisk behaves strangely from time to time.