Frisk

Abilities
Frisk is incredibly agile, and is capable of dodging most fair attacks. Frisk, however, has no capability to hurt people on purpose, at a LOVE (Level Of ViolencE) of 1 (the lowest level possible). Frisk's SOUL modes have different functions.

Blue Mode, caused by Papyrus and Sans, causes Frisk's SOUL to have a gravity effect on the bullet board.

Green Mode, caused by Undyne, grants Frisk a shield to defend themself.

Yellow Mode, used by Frisk when they activate it on their cell phone, allows Frisk to fire yellow pellets straight upward to destroy bullets.

Purple Mode, caused by Muffet, the spider-girl from Hotland, causes Frisk's SOUL to move about on three tracks.

With the power of their determination, Frisk is actually able to reset the timeline they are in to an earlier state, usually one in which they are filled with a significant amount of determination. Obviously this happens when Frisk is killed, as they have already been killed twice in Dimensional Clash.

Personality
Frisk is a kindhearted, sweet child who is completely pacifistic. In the Pacifist Ending of UNDERTALE, characters such as Asriel make emphasized note about Frisk's kindness, understanding, and grace. This is also the only ending when Frisk's name is given, which implies that this is their true character and personality.

Frisk talks to other characters, but unless the player receives a prompt on what to say, their dialogue is not shown. During battles, the flavor text describes what Frisk says. Outside of battle, when Frisk speaks on their own, the other character's dialogue box displays "..." to indicate them listening to Frisk.

Frisk uses they/them/theirs pronouns since their gender is ambiguous in UNDERTALE.

Bio
One day, a human fell through the barrier within Mt. Ebott and landed in a bed of flowers. Despite a flower's insistence that the world of the Underground was "kill or be killed," that human went on to befriend every monster that lived in the Underground, going out of their way to spare them and share in their hopes and dreams. Even when their caretaker Toriel insisted that they learn to fight, they refused to strike. Even when faced with relentless killers, the human, stalwart in their notions of mercy, never gave up, due to the sheer weight of their DETERMINATION. Even when the limits of their kindness were tested, even when monsters actively tried to kill them, the human never wavered.

On their adventure, they made many friends. Papyrus and Sans, the border-patrol skeleton brothers. Undyne, the greatest hero of all Monster-kind. Dr. Alphys, a nerdy lizard scientist obsessed with anime, and her robot Mettaton, a show-bot with fantastic legs and a charismatic personality.

They even befriended the desperate king ASGORE, as well as the very flower that wanted to kill them in the very beginning.

That human is Frisk.

Actions in Roleplay
Frisk is first seen in Wahi, having fallen into a chasm where a Muaka and a Kane-Ra (the latter of which had just been fought by Robin). Frisk befriends both Rahi beasts and rides them to the day camp that the Criminal Revolution Militia had set up.

Many of Frisk's significant actions happen with the C.R. militia. Frisk plays a game of poker with Eric, Bill (Eric's brother), and some other players, before it all goes to complete chaos when the evil Toaster eggs Eric on to kill Frisk for winning. Frisk dies, then resets with their determination. Frisk shows respect for Bill after Eric accidentally shoots Bill. This allows Frisk to SPARE Eric, and nets them the Sawed-off Shotgun.

Which Frisk later fires a blank out of to wake Robin up and show her the Locusts.

Trivia

 * Frisk has not been much subject to japes, but Frisk has been referred to as "frick" and "fisk".