Eight Humans

The eight humans are the only humans from the surface who have fallen through the Barrier on Mount Ebott into the Underground. Among them are the First Human, the protagonist, and the six human SOULS that Asgore has collected.

Each SOUL Mode and colored Attack Type correspond to one of the Eight Humans.

Main Story
Prior to the events of the game, seven human children fell into the Underground and died.

The first human to fall was Chara, who was found and then befriended by Asriel. Later they were adopted by Toriel and Asgore as a second child. One day, Chara became deathly ill; their last request was to see the Golden Flowers from their village, but they could not be brought through because of the barrier, and died in the Underground. Asriel absorbed their SOUL and crossed the barrier to Chara's village, where he was lethally wounded. Asriel died shortly after he returned to the Underground.

The deaths of his children lead Asgore to declare war on humanity. He also decreed to kill any human who fell into the Underground, and have their SOUL collected to destroy the barrier.

Sometime after then and before the start of the game, six additional humans climbed Mount Ebott and fell into the Underground; each with their own associated items and mysterious reasons. Every one of these six humans was killed, and their SOULS were stored for use by Asgore. Their bodies were kept in coffins near Asgore's throne room.

The protagonist is the Eighth Human to fall. Before fighting with Undyne, they are told about the six humans who had their SOULS taken, and that their SOUL will be the seventh and final one required to break the Barrier.

Neutral Route
In New Home, the coffins where the previous human's bodies were kept can be found. The first human's coffin is empty, as Toriel took their body with her to the Ruins when she left New Home. Chara's body was buried under the flower patch the protagonist falls onto at the beginning of the game.

At the end of the route, Asgore reveals the six SOULS he possesses right before attacking the protagonist. After he is defeated, Flowey absorbs the SOULS to become a powerful creature, Photoshop Flowey.

During the fight against Photoshop Flowey, the six SOULS and their items appear to attack the protagonist one at a time. When the protagonist calls for help through the ACT option, the SOUL will assist them with green attacks, which heal them. After calling for their help, the six SOULS reduce Flowey's defense and send green attacks to the protagonist. After he is defeated, the six SOULS revolt against Flowey, taking away his powers and leaving him helpless to the protagonist.

After the credits, Sans tells the protagonist that the SOULS have disappeared, precluding the plan of breaking the barrier with them.

Genocide Route
Near the Genocide Route's end, Alphys urges Asgore to absorb the six SOULS.

At the end of the route, Chara appears in person to speak with the Player. They tell them they were brought back to life thanks to the player's determination, and that the purpose of this reincarnation was power. Chara then proposes the player to erase the world. Regardless of their choice, they attack the screen and destroy the world, which closes the game. Upon launching it again, the player only sees a black void; Chara will appear and offer to recreate the world in exchange for the player's SOUL.

True Pacifist Route
Toriel points out to Asgore that the six humans who were killed in the Underground could have been spared, if he absorbed a single SOUL to cross the barrier and then collected six more to break it.

Flowey absorbs the six human SOULS and all of the monsters' SOULS to regain his form as Asriel. He then turns into his "God of Hyperdeath" form, and fights the protagonist while mistaking them for the first human. At the end of the fight, Asriel destroys the barrier and releases the SOULS, liberating everyone from the Underground. After this, the seven coffins near Asgore's throne room are found open, either to prepare the humans' bodies for burial or indicating that the humans had been restored to life with the return of their SOULS.

List of Human SOULS
During the Photoshop Flowey fight, the SOULS attack the protagonist with weapons found throughout the game in order. When playing the Ball Game, the protagonist may achieve any of seven flag colors, all with a different message and each corresponding to one of the SOUL colors (Red, Orange, Yellow, Green, Light Blue, Blue, Purple).

The following is a list of SOUL colors and the details associated with them.

Red SOUL

 * Associated Items:
 * The Eighth Human (Frisk):
 * (Beginning of Game) Stick and Bandage, the items that the protagonist starts with.
 * The First Human (Chara):
 * (Neutral Route) Worn Dagger and Heart Locket in Asgore's Home.
 * (Genocide Route) Real Knife and The Locket in Asgore's Home.
 * Combat Mechanics:
 * Normal Mode: Free movement. Sprouts legs when running away.
 * Snowball Game Text: Try as you might, you continue to be yourself.
 * Owners: The first human, Chara; the eighth human, Frisk.

Light Blue SOUL

 * Trait: Patience
 * Associated Items: Toy Knife and Faded Ribbon found in the Ruins.
 * Combat Mechanics:
 * Light-Blue Attacks: Inflicts damage unless the SOUL does not move.
 * Photoshop Flowey: Attacks with Spinning Blades. Heals with Bandages.
 * Snowball Game Text: "Ball" is "Small". You waited, still, for this opportunity... then dethroned "Ball" with a sharp attack.

Orange SOUL

 * Trait: Bravery
 * Associated Items: Tough Glove and Manly Bandanna from Snowdin Shopkeeper.
 * Combat Mechanics:
 * Orange Attacks: Inflicts damage unless the SOUL moves through them.
 * Photoshop Flowey: Attacks with Spinning Gloves with Eyes. Heals with Thumbs Up.
 * Snowball Game Text: You are the kind of person who rushes fists-first through all obstacles.

Blue SOUL

 * Trait: Integrity
 * Associated Items: Ballet Shoes and Old Tutu in Waterfall.
 * Combat Mechanics:
 * Jump Mode: Gravity affects the SOUL, with the SOUL falling back to the bottom of the box after a jump.
 * Photoshop Flowey: Attacks with Ballet Shoes and Stars. Heals with Music Notes.
 * Snowball Game Text: Hopping and twirling, your original style got you through.

Purple SOUL

 * Trait: Perseverance
 * Associated Items: Torn Notebook and Cloudy Glasses from Gerson.
 * Combat Mechanics:
 * Trap Mode: The SOUL's movement is restricted to 3 horizontal purple lines.
 * Karmic Retribution: Inflicts Sans's Karmic Retribution (KR) poison damage.
 * Photoshop Flowey: Attacks with Books and Negative Words. Heals with Positive Words.
 * Snowball Game Text: Even when you felt trapped, you took notes and achieved the end of "Ball".

Green SOUL

 * Trait: Kindness
 * Associated Items: Burnt Pan and Stained Apron from Hotland.
 * Combat Mechanics:
 * Shield Mode: Standing still and shielding from Undyne’s spears.
 * Green Attacks: Heals you and/or progresses the battle.
 * Platforms: When the SOUL is in Jump Mode, it may jump on the platforms from under or the side of the platform, and keep the SOUL elevated.
 * Photoshop Flowey: Attacks with Frying Pans and Fire. Heals with Eggs.
 * Snowball Game Text: Your care and concern for "Ball" brought you a delicious victory.

Yellow SOUL

 * Trait: Justice
 * Associated Items: Empty Gun and Cowboy Hat from Bratty and Catty.
 * Combat Mechanics:
 * Shooter Mode: SOUL is turned upside down, and shoots bullets upward. Can be used to damage foes and objects.
 * Photoshop Flowey: Attacks with a Loaded Gun. Heals with Four-Leaf Clovers.
 * Snowball Game Text: Your sure-fire accuracy put an end to the mayhem of "Ball".