Love is perhaps the most powerful ancient enchantment, with the potential to counteract the Dark Arts and transform lives.
References from the canon
- The meaning of Love is studied behind locked doors in the Department of Mysteries. The Love Room contains a fountain of powerful love potion to aid in research ( PC/JKR2, OP37). When Harry tried to open the door with a special knife Sirius gave him, the knife blade melted from the heat (DH34).
- Love is so powerful it can protect beyond death. Harry Potter's mother Lily sacrificed herself to save him, and that selfless act imbued him with magical blood so that he could not be harmed or even touched by anyone cursed, such as Lord Voldemort (PS17, OP36). When Harry sacrificed himself for the friends he loved during the Battle of Hogwarts, he came so close to death that the Horcrux departed from his scar, thus diminishing Voldemort's power while increasing his own (DH34, DH35, DH36).
- A coporeal Patronus often changes over time to reflect a deep abiding love (Pm, BLC). Tonks Patronus changed from a jackrabbit to a wolf when she fell in love with werewolf Remus Lupin (Pm, HBP8). Severus Snape always kept the same silver doe Patronus as the love of his life, Lily Evans (DH33, DH36).
- Love is a powerful countercurse to the Dark Arts. When Ilvermorny School was attacked by evil witch Gormlaith Gaunt, her Curse of Enchanted Slumber could not keep Isolt and her husband James asleep after they heard their young children crying in fear (Pm). Harry Potter's grief after the death of his friend Dobby the House-elf protected him from the effects of the Horcrux in his forehead scar, making the vicious Voldemort seem further away, "like a distant storm ... across a vast, silent ocean" (DH24).
- Dumbledore's Deluminator seemed to channel the power of love to help Ron find his way back to Harry and Hermione in the Forest of Dean (DH19). A hot ball of bluish light, like that from a portkey, appeared after he heard Hermione's voice coming from the Deluminator. The light entered Ron's heart and he suddenly knew where to apparate.
Rowling makes it clear that love is not always a pure force for good. The Bloody Baron killed the object of his affections, the Gray Lady of Ravenclaw, then killed himself out of remorse, turning them both into ghosts forever (DH31). Bellatrix Lestrange loved Voldemort in the manner of a twisted obsession, especially considering that she still had a husband, and she was willing to sacrifice her own nephew, Draco, for the Dark Lord (HBP2, BLC). Dumbledore's short-lived infatuation with Gellert Grindelwald led to the tragic death of Arianna Dumbledore, and long-term problems between Albus and his brother Aberforth (DH28, DH35).
And while Wizards may use love potions for research at the Department of Mysteries, they do not produce real or long-lasting love (HBP9). Merope Gaunt tricked the Muggle Tom Riddle into marrying her with a love potion, but he was quick to abandon both her and her unborn son when he found out the truth (HBP13). With love, there are no shortcuts or substitutes for the real thing.