There is only good when there is evil. And oftentimes, that evil is ugly and disoriented, even frightening to look at. Fans of the Harry Potter franchise will agree that the Dark Lord Voldemort fits that description perfectly, haunting children's nightmares since they first saw him on the back of Professor Quirrell's head in Harry Potter and the Sorcerer's Stone.
It took another three movies/books for You-Know-Who to take the form of a full body, and he was arguably even more terrifying as he stood tall over Harry and his spell-casting comrades. His ghoulish presence grew ever more powerful when the legend, that was once just part of a tale of darker times, was reborn in the physical form with reptile-like features.
But Voldemort wasn't always the pale-skin, serpent-faced villain that viewers came to fear for so long. At one point, Voldemort looked like just any other wizard, and even particularly handsome, as well. So, what happened? How did an exceptionally intelligent, good-looking student at Hogwarts become such a force of evil to the point that he even looked the part by the end of the Harry Potter saga? Turns out, dabbling in the Dark Arts does quite the number on one's physique.
What Did Voldemort Look Like Originally?
He-Who-Must-Not-Be-Named was born Tom Marvolo Riddle, a half-blood -- his father Tom Riddle Sr., a muggle, and Merope Gaunt, his witch mother. According to the stories of his childhood, Merope was particularly unattractive due to generations of inbreeding, giving her a "rather heavy face" and a lazy eye. But Tom Sr. was known around town as being a dark-haired heartthrob with whom Merope desperately wanted to be with in the hopes that their child would grow to be as beautiful as his father.
With the help of some spells and potions, Merope tricked Tom Sr. into conceiving a child together. But once he fell out of the trance, he abandoned the witch and left her alone to raise the future leader of the Death Eaters. But Merope's motherhood was short-lived as she died not long after giving birth to little Tom. However, her desire to have a handsome child was met, as Tom not only grew to be as good-looking as his father, but he managed to use his inherited attributes to his own devious advantage.
It's unclear how early in his life Tom used his good looks as a tool, but he was cited to have lured other children from his orphanage to places like caves and such, despite the eerily disturbing reputation he had created for himself. It can be so that Tom's natural attractiveness, even as a young boy, helped give him a trustworthy face that encouraged other children to approach him without any suspicion. But, it wasn't until he grew older and his evil goals became clearer that Tom decided that the only blessing he received from his muggle father was how he looked.
As Tom became more and more fascinated with the Dark Arts, he began fiddling with the concept of immortality. He would read up and practice dark magic in private before acquiring his own followers who wished to do the same. By the time he was graduated from Hogwarts, he asked Albus Dumbledore if he could be the school's Defence Against the Dark Arts professor, to which Dumbledore denied, having had growing suspicions of his evil desires since the day het him in the orphanage so many years prior. This only fueled Tom more to want to be the most powerful wizard in the world, and he finally figured out a way to achieve immortality: the horcruxes.
Tom adopted his alter ego, Lord Voldemort, and began his expedition to eternal life. By using the horcruxes and splitting his soul into seven, he knew that even in his physical death, his spirit would still live. Two of the horcruxes he used were a locket of Salazar Slytherin and a cup of Helga Hufflepuff, both of which he found in the possession of the elderly Hepzibah Smith. His method in which to steal the two Hogwarts artifacts was to woo Hepzibah and grow closer to her before poisoning her and stealing the artifacts for his own. Tall, pale, and with dark eyes and hair, the poor old woman couldn't resist such attention and fell into his trap. Although his plan was coming together, he was unaware of the toll it would take on his body.
Why Did Voldemort's Appearance Change?
Tom's journey to immortality continued as he sought the horcruxes to spread his everlasting soul across the world. As a result, his soul was continually breaking, but so was the body that it once inhabited. So, as the soul of Tom Riddle was escaping his body piece by piece to reside in a new host, the identity that was once the orphan boy was slowly dying and becoming something entirely new, both physically and spiritually.
Tom's eyes became permanently bloodshot and his skin grew paler with every murder he committed and with every horcrux he used. By the time he obtained six horcruxes, he was no longer recognizable as Tom Riddle, rather, he had become the Dark Lord Voldemort entirely, through and through. But in trying to destroy the prophecy of his downfall -- Harry Potter -- his forbidden curse rebounded against baby Harry and killed the host in which the remainder of Voldemort's soul lived. However, pieces of his soul lived on, one of which found itself inside Harry himself.
For the years to come, Voldemort lived as a sort of spirit before latching onto Professor Quirrell's head and feeding on unicorn blood just to stay alive. But after Quirrell perished, the conniving Peter Pettigrew took it upon himself to resurrect the You-Know-Who. Through dark magic, Pettigrew managed to formulate a concoction that would give Voldemort a physical host in the form of a deformed, scaly-looking infant body. And eventually, with another potion, mixed with the blood of an enemy, the bone of a father, and the flesh of a servant, Voldemort was reborn into the body that viewers know him as best.
Besides the unpredictability of dark magic remedies, it is not entirely clear as to why Voldemort's new body resembled a snake -- with reptilian slits for nostrils, his eyes that of a serpent's, and his skin as pale as a ghost. Some fans allude it to the fact that one of his horcruxes is the python Nagini and so his newest physical form would reflect the bodies in which his soul inhabits. In addition, Voldemort had spoken parseltongue his entire life, even before he knew he was a wizard. On his mother's side, Voldemort was also a descendant of Salazar Slytherin, so snakes have always been a companion to the Dark Lord.
So, throughout the stories of Harry Potter, Voldemort's acts of terrorism and dark magic, the many breakings of his soul, and the methods in which he chose to be resurrected, had caused his appearance to drastically change as a direct result of what was in his heart: evil.