Frisk has the soul of Determination and is the protagonist/player role.
Frisk is pretty much like the player, but has their own traits as well. You shouldn't put them near Chara, as they will beat her with a stick for wanting to do genocide.
From the whole game) They look like classic Frisk, but they have brown fur, with a muzzle the same as Frisk's skin color. They have the same blue jumper with pink stripes and brown shoes.
They have their own stick and their own knife, they can also spin dash, and roll up into a ball.