- "There is a room in the Department of Mysteries that is kept locked at all times. It contains a force that is at once more wonderful and more terrible than death, than human intelligence, than the forces of nature. It is also, perhaps, the most mysterious of the many subjects for study that reside there. It is the power held within that room that you possess in such quantities and which Voldemort has not at all."
- —Albus Dumbledore to Harry Potter about love[src]
Love is a deep, powerful, and ineffable emotion of attachment to, and affection for, another being or beings. It gives those who experience it the ability to do very great things. Someone full of hate, such as Tom Riddle who has never known it even once in their entire life, cannot understand love's full magical properties. Love is one of the hardest and strongest kinds of magic, and as such there is a room devoted to the study of it in the Department of Mysteries. Love is also quite possibly the most mysterious branch of magic and is extremely difficult to comprehend.
In 1925, Merope Gaunt had fallen deeply in love with Tom Riddle, and betrayed her family's beliefs in blood purity to be with her love. She used a Love Potion in order to attract Riddle to her, but ceased feeding him it once she was pregnant, thinking that Tom would finally love her in return, or at least stay for their unborn child out of love for it, of which Tom did neither. The usage of a love potion for Tom Riddle Jr.'s conception is symbolic for his inability to understand love for his entire life, as it was due to coercion rather than true love.
- "The Boy Who Lived. How lies have fed your legend Harry. Shall I reveal what really happened that night thirteen years ago? Shall I divulge how I truly lost my powers? Yes, shall I? It was love. You see, when dear sweet Lily Potter gave her life for her only son...she provided the ultimate protection. I could not touch him. It was old magic. Something I should have foreseen. But no matter, no matter. Things have changed. I can touch you...now!"
- —Voldemort reflecting on his first defeat[src]
In 1981, Severus Snape's love of Lily Evans pushed him to join the Order of the Phoenix, even though he hated her husband, and then Snape begged Lord Voldemort to promise to spare her when he went to kill her son Harry.. In that same year, Lily's love for her son Harry protected him against Lord Voldemort. He became the only known person in history to survive the Killing Curse because of the power of her loving sacrifice. However, it could be that while love was the motive, the cause of Harry's protection was that Lily had lured Voldemort into a binding magical contract so that having killed her, he would be unable to kill Harry, because he had already promised to spare Lily, and only her offer allowed him to kill her.
After Barty Crouch Jr. was imprisoned in Azkaban, his mother persuaded his father to help break him out. Crouch Sr. agreed out of love for his wife, even though he did not love his son at the very least.
In 1992, Because of the protection that Lily Evans's death created for Harry Potter, Professor Quirinus Quirrell could not touch Harry without serious harm to his physical well being. In doing so, this lead to Professor Quirinus Quirrell's death and Voldemort was once again without a body to possess.
In 1996, his love for Sirius again helped him, when his grief over his godfather's death pushed Voldemort out of his mind. In that same year, Dumbledore ignored Harry, thinking that this would prevent Voldemort from using the connection with Harry Potter to gain insight into his own mind, because Voldemort would sense he cared "too much" about Harry and would be eager to use their relationship to gain access to Dumbledore's mind and knowledge of the activities of the Order of the Phoenix.
In 1997, Harry Potter's love for Ginny Weasley was shown when he entered into the common room after the Quidditch match that took place during his detention with Professor Snape and ended up kissing her, and it also drove him to leave her in fear of her being a target of Lord Voldemort. In that same year, Harry's love for Professor Albus Dumbledore pushed him to attack Severus Snape with one of his own spells. Draco Malfoy's love for his family pushed him to attempt to kill Dumbledore, even though he really did not want to. Fleur Delacour asserted her love for Bill Weasley even after he was horribly scarred in battle by Fenrir Greyback. Her declarations prompted Tonks to once again impress upon Remus Lupin she did not care about his being a full werewolf, older than her, or that he was poor, that she loved and wanted to be with him anyway.
Their love for Harry motivated Hermione Granger and Ron Weasley to accompany him on the Horcrux hunt, leaving their families and risking their lives. When the Harry, Ron and Hermione were taken to Malfoy Manor, Ron begged Bellatrix to interrogate him instead of Hermione because he deeply loved her.
During the Battle of Hogwarts, Lucius and Narcissa Malfoy's love for their son motivated them to look for him instead of fighting. Ron and Hermione began in the battle one of the most powerful relationships in wizardkind. In the end, Harry's love finally destroyed Lord Voldemort once and for all. Harry's love for his friends and love ones caused him to sacrifice himself to Voldemort. This love was what made Harry different from the powerful Voldemort. He had something worth fighting for while Voldemort could never understand the power of love. Harry's love for people even made him offer Voldemort a final chance of redemption.
Love in literature
- Amata fell in love with a Muggle named Sir Luckless.
- Cadmus Peverell was so in love with his dead lover, that he killed himself so he could finally join her.
- The Bloody Baron loved the Grey Lady (Helena Ravenclaw) and killed himself after he killed her in a rage.
- The Warlock in The Warlock's Hairy Heart regarded love as a sickness, therefore he paid dearly for it.
Love and magic
Love has a profound effect on magic. Lily Evan's love for her son made her willing to die for him, and because of that sacrifice, Harry was protected from the most powerful Dark magic of all — the Killing Curse. Love is the only protection against the lure and power of the Dark Arts, which are fueled by hateful emotions. Harry failed to learn Occlumency in order to block his connection to Lord Voldemort's mind, but he managed to block the link when he focused on his feelings for his loved ones, such as when he felt grief over his godfather's death and when he was frantic with worry about Hermione Granger when she was being tortured by Bellatrix Lestrange.
- "Your mother died to save you. If there is one thing Voldemort cannot understand, it is love. He didn't realize that love as powerful as your mother's for you leaves its own mark. Not a scar, no visible sign ... to have been loved so deeply, even though the person who loved us is gone, will give us some protection forever. (...) It was agony to touch a person marked by something so good."
- —Dumbledore on why Quirinus Quirrell could not touch Harry[src]
Love can also affect other types of magic, notably the Patronus. Harry's Patronus is the same as the Patronus and Animagus form of his father, a stag. James' wife had a doe Patronus to match her husband's, and Severus Snape's mimicked hers because of his love for her. Nymphadora Tonks's Patronus changed to a werewolf when she fell in love with Remus Lupin.
- "Hermione was screaming again: The sound went through Harry like physical pain. Barely conscious of the fierce prickling of his scar, he too started to run around the cellar, feeling the walls for he hardly knew what, knowing in his heart that it was useless.... He felt Voldemort’s fury, but as Hermione screamed again he shut it out, returning to the cellar and the horror of his own present."
- —Harry Potter cutting off his connection to Voldemort[src]
Love Potions, like Amortentia, and Entrancing Enchantments, are meant to artificially create love, but they cannot; nothing can reproduce love. Instead, they can at most produce an intense infatuation. When a person smells Amortentia, they will smell things that remind them of what and who they love. Within the love room of the Department of Mysteries is where love is being studied, and a large fountain of Amortentia is kept.