The Frankenstein Monster, also called "The Creature" or sometimes simply "The Monster," was the creation of the Swiss medical prodigy Victor Frankenstein. Victor's studies while at university delved into the secrets of life and death, and he decided to try and give life to something that had never been truly alive. He fashioned a human body by stitching together parts from multiple corpses. Telling his story to Captain Robert Walton, Victor refused to explain precisely how he'd brought the body to life, fearing that Walton would try and repeat his experiment.
The Monster was a very large, physically ugly man. While he worked on it, Victor had been so blinded by his obsession he'd refused to see how ugly his creation actually was. Only after the elation of his successful experiment wore off did he realize the horrifying truth, and fled his laboratory, and fell asleep on his bed. The Monster, possessing a childlike personality initially, came into the room and approached his "father." Wakening, Victor fled in horror, abandoning his creation. When he returned later with Henry Clerval, the Monster was gone, having taken the only clothing to hand, Victor's coat, and gone out into the world.
He was shunned wherever he went for his ugliness. Even when he saved a child from drowning in a river, he was shot in the shoulder by her terrified father, and forced to flee. He found a brief friendship with a blind man named De Lacey, and lived near him and his family, often doing kind deeds for them. Spying on the family, he learned English because De Lacey's son Felix's wife Safie was Turkish; as her in-laws taught her English, the eavesdropping Monster learned it, too. When he actually approached the family to make friends, they fled in terror from him. Enraged, he burned down their house.
By now, the Monster had found Victor's notebook of his experiments in the pocket of the coat he'd taken from Victor's house. He taught himself to read, and, consulting the notebook, learned of how he was created and also Victor's name. He sought Victor out and argued with him, expressing outrage at his creator abandoning him to an uncaring and hostile world, and demanded Victor make a mate for him, someone like him, who wouldn't find him ugly. At first, Victor agreed. But when the Monster visited his laboratory to check on his progress, he reneged and tore up the half-finished body of the female creature. The Monster vowed revenge.
He took his revenge, murdering Victor's younger brother William and framing Justine Moritz for the crime, for which she was hanged. He also strangled Henry Clerval to death, a crime for which Victor himself was nearly condemned, and finally, on Victor's wedding night, he killed his creator's new wife Elizabeth. This indirectly also led to the death of Victor's father of a broken heart. His revenge complete, the Monster fled to the arctic. His enraged creator pursued him, and eventually died.
By now feeling guilty for his campaign of vengeance, the Monster slipped aboard Captain Walton's ship to see the dead Victor's body. Walton came in and confronted him, but the Monster assured Walton he would work no more evil. He would commit suicide. Before Walton could stop him, he jumped overboard and was carried away into the darkness on an ice floe. An undetermined amount of time later, he built a funeral pyre and burned himself alive.