Lily's sacrifice saved more than just her son in Harry Potter. Through events following the Potters' deaths, several other people were affected by Lily Potter's decision to stand unarmed in the way of her son's murder. The most obvious beneficiary was Harry, who survived Voldemort's Killing Curse thanks to the protection Lily's death provided. However, there were more who indirectly had their lives saved by Harry Potter's mother than just The Boy Who Lived.
The Dark Lord had come to believe through a prophecy in Harry Potter that a boy born at the end of July would one day rise to defeat him. Of course, he identified the Chosen One to be Harry, and the rest is history. Years later, Dumbledore impressed on Harry the importance Lily's sacrifice had for his and Voldemort's destiny. It wasn't Harry's power that destroyed Voldemort's body and kept the Boy Who Lived alive. Instead, it was the strength and love of his mother, Lily Potter. Though she never intended it, her death created a chain reaction that achieved more than just protecting her son's life.
4 Lily Potter's Sacrifice Also Saved Neville Longbottom
The nuances of Lily's death meant that Voldemort could not harm her son, but there was another child who was saved. Neville Longbottom had also been born at the end of July, and as the prophecy said, both his parents had "defied" the Dark Lord, as they were of the Order of the Phoenix. However, in the years before Harry Potter, Voldemort determined that the Longbottoms were less likely, and the Potters were selected instead.
Still, it's unlikely that Voldemort would have allowed any room for error. Dumbledore explained in Harry Potter and the Half-Blood Prince that Voldemort planned to use Harry's murder to create his last Horcrux (something that didn't go to plan). But, after he was done, he would have killed Neville as well, just to be safe. In fact, when Voldemort disappeared, his Death Eaters only had one lead to find him, which was why they tortured Frank and Alice Longbottom. Ultimately, if Lily hadn't sacrificed herself to save Harry, Voldemort's subsequent planned murder would have become a reality.
3 Severus Snape's Soul Was Saved By Lily Potter's Sacrifice
In Harry Potter and the Half-Blood Prince, Harry learned that Severus Snape had been the one to relay the contents of Trelawney's prophecy to Lord Voldemort. Harry had already hated his Potions Master, but the revelation that he had been partially to blame for James and Lily's murders enraged him. Of course, he didn't know at this point that Snape had once been Lily's best friend and that his involvement in her death hurt the double agent himself.
When Lily was at school with Snape, she gave him a choice between their friendship and the Dark Arts. Unable to turn away from the promise of power, Snape chose to pursue Voldemort and the Death Eaters. Of course, he couldn't have known that this choice would eventually lead to Lily's death, and even though he still despised the son she had had with his enemy in Harry Potter, James, he vowed to protect him no matter the cost.
That cost was Severus Snape's life. He gave Harry the information he needed to willingly sacrifice himself and thus survive Voldemort's Killing Curse—but was killed before he could see the Dark Lord defeated. Still, Snape died redeemed of his decision to choose darkness over Lily's life. He treated Harry terribly and could never get over the fact that the boy was a living reminder of Lilly's marriage to James Potter, but he did his job and kept him safe. Lily's death may have been the worst event of Snape's life, but it was the final step that led him away from the Dark Arts and toward redemption after working with the Order of the Phoenix.
2 Lily Potter's Sacrifice Protected Harry From Voldemort's Embedded Soul
Clearly, Harry's life was saved on multiple occasions because of Lily's sacrifice. It was because of his mother that Harry survived the Killing Curse when he was a baby, and that same loving protection kept Voldemort from murdering him in the Forbidden Forest in Harry Potter and the Deathly Hallows. However, there was another, less obvious way that Lily's love guarded Harry against harm. As referenced in Half-Blood Prince, Dumbledore told Harry that few others could have resisted turning to evil if they had the kind of connection to Voldemort he did (later revealed to be Voldemort's soul):
“It is essential that you understand this!” said Dumbledore, standing up and striding about the room, his glittering robes swooshing in his wake; Harry had never seen him so agitated. “By attempting to kill you, Voldemort himself singled out the remarkable person who sits here in front of me, and gave him the tools for the job! It is Voldemort’s fault that you were able to see into his thoughts, his ambitions, that you even understand the snakelike language in which he gives orders, and yet, Harry, despite your privileged insight into Voldemort’s world (which, incidentally, is a gift any Death Eater would kill to have), you have never been seduced by the Dark Arts, never, even for a second, shown the slightest desire to become one of Voldemort’s followers!” -Harry Potter and the Half-Blood Prince
Dumbledore explained that this was all thanks to Lily's sacrifice. In Harry Potter and the Order of the Phoenix, Voldemort attempted to possess Harry's body but could not because of Harry's love. Similarly, the fragment of Voldemort's soul in Harry was never able to gain complete control because the presence of Lily's love was too strong for it to overcome. Dumbledore clarified that it was precisely this that made Harry the Chosen One. By murdering Lily, Voldemort made Harry the only secure vessel for his soul fragment and, therefore, the only person to defeat him.
1 Lily Potter's Sacrifice Saved The Entirety Of The Wizarding World
Of course, since Harry was only alive to defeat Lord Voldemort in Harry Potter and the Deathly Hallows because of Lily's sacrifice, it can be said that the entire wizarding world owes their lives to her as well. If she hadn't stood between Harry and Voldemort that fateful Halloween, Voldemort would have killed Harry and likely continued on his way to leading the wizarding world down a dark path. However, it goes much further than this. Lily's love was the center of Harry's power, so in a sense, she was the true Chosen One.
The prophecy foretelling the coming of the Chosen One was misleading because it spoke only of the boy. It stated that he would have "power the Dark Lord knows not," but this was never Harry's power. Harry was only a baby when Voldemort attacked, incapable of feats of great magic. It was Lily's bravery that made all the difference. She had no wand and no hope for survival but openly faced death. She may not get much of the credit, but when it comes down to it, Lily was the true hero of the Harry Potter series, not her son.
