Asgore Dreemurr

Lord Asgore Dreemurr is the ruler of the the Underground, and it is denizens, Monsters. He is the ex-husband of Toriel and the father of Asriel Dreemurr.

Appearance
Asgore is a large goat-monster with an incredible shoulder span. He has a full yellow beard, as well as two horns. He appears to wear a suit of armor as well as a blue cape with yellow pauldrons. Asgore sports a small crown atop his head as well.

Personality
He is depicted as a kind and loving family man, although in Undertale he has several difficult decisions to make, which he disagrees with morally, but feels compelled to enact. This burdens him heavily. Asgore is also shown to be chivalrous, kneeling infront of the player after being defeated.

Main Story
Asgore and Toriel were originally married as King and Queen of the Underground, after being cast out from the Surface after the War. They eventually had a son, Asriel, as well as a second adopted child, the first human to ever fall through the Barrier. However, this human eventually grew sick and died, all while Asriel was still young. Asriel ended up forming with the human's soul, and carried him past the Barrier back to his village. He sustained heavy attacks from the humans on the surface and ended up dying when he returned to the Underground.

This tragedy drew Asgore to the conclusion that all humans are dangerous, and decided to kill and harvest the soul of any human that falls through the barrier, so that he could gather the Seven Souls to become strong enough to destroy the barrier. Toriel was appalled by this grotesque decision, and forfeited her right as queen, divorced Asgore, and went to live in the Ruins, where she would care for any humans that fell through the barrier.

Between then and the start of the game, six additional humans fell through the barrier on Mount Ebott into the ruins, all of which Asgore eventually reaped the souls of.

Neutral Route
After travelling through New Home and arriving in the Throne Room, Asgore greets the player. He comforts them as he brings them to the barrier, where he gives them time to finish anything they still wish to do before fighting. He then destroys the mercy button and fights the player. After being defeated, the player has the choice to spare or kill him. If he is spared, Flowey appears and finishes Asgore off, stealing the six human souls that he revealed prior to the fight. However, if the player instead decides to kill him, before they can finish off his soul, Flowey lands the final blow, noting how Frisk has finally realized how this is a 'kill-or-be-killed' world, and steals the six human souls.

Pacifist Route
When the throne room is reached, Asgore greets the Protagonist, and comforts him as he brings him to the barrier, where he gives him time to finish anything he still wishes to do before fighting him. He then initiates combat with the player, but is interrupted by Toriel, who states how awful it is that he could seek to hurt an innocent creature such as the Protagonist. Then the other Boss Monsters which the player has befriended arrive, and begin conversing, until Flowey appears, having stolen the six human souls, and begins to promptly steal the souls of the Boss Monsters as well.

Flowey, fit with all of those souls, returns to his original form - Asriel Dreemurr. He then battles the player. After the battle is over, and the Protagonist is victorious, they convince Asriel to stop his plans, leading Asriel to destroy the Barrier and release the souls which he took into himself.

Asgore can be seen finally in the epilogue, asking the Protagonist if they would become the ambassador for monsters to humanity on the Surface.

Genocide Route
When the throne room is reached, Asgore makes a comment that implies that Flowey has spoken to him prior to the player's arrival; the player initiates combat and goes on to deplete his entire health bar with a single blow. Flowey returns to land the final hit as an attempt to appear loyal and useful to Frisk, however this fails and Flowey is promptly killed.

Toriel
His ex-wife, he wishes to befriend her, which she refuses. Before they separated, they used to be "insufferable together", as described by the Turtle Shopkeeper in Waterfall. Toriel is disgusted by his actions to harm humans (which caused her initial departure).

Trivia

 * Dreemurr, when rearranged, can be spelled as murderer.
 * Asgore wields a red trident during his fight. Being a goat monster with a red trident, it is a possible reference to Satan.
 * Asgore, as seen in the scene before the battle with Asriel and the ending, seems to still have a complicated relationship with his ex-wife Toriel.
 * Asgore is also known as King Fluffybuns, a nickname given to him by Toriel.
 * If you consume Toriel's pie in his boss fight, it reminds him of her and lowers his attack and defense.