Offer magi har en omedelbar skyddande effekt.
Lily offra sig för att rädda Harry hade en omedelbar effekt utan att någon behöver göra ytterligare magi - det skydde Harry från den mörka Herrens dödsförbud.
“Voldemort laughed softly in his ear, then took the finger away, and continued addressing the Death Eaters. ‘I miscalculated, my friends, I admit it. My curse was deflected by the woman’s foolish sacrifice, and it rebounded upon me.”
- Harry Potter and the Goblet of Fire, Chapter 33 (The Death Eaters)
Harry kunde på samma sätt "skydda" alla genom att villigt dö för dem. Hennes offer gjorde det också, så att den mörka Herren inte kunde röra Harry, som också hände "automatiskt" utan att det krävdes ytterligare magi för att åberopa det.
“You all know that on the night I lost my powers and my body, I tried to kill him. His mother died in the attempt to save him – and unwittingly provided him with a protection I admit I had not foreseen … I could not touch the boy.”
- Harry Potter and the Goblet of Fire, Chapter 33 (The Death Eaters)
Det är oklart om Harrys offer också gjorde det så att den mörka Herren inte kunde röra alla andra, men det skydde dem alla från den mörka Herrens attacker. Det är den här omedelbara effekten som Harry hänvisar till.
“You won’t be killing anyone else tonight,’ said Harry as they circled, and stared into each other’s eyes, green into red. ‘You won’t be able to kill any of them, ever again. Don’t you get it? I was ready to die to stop you hurting these people –’
‘But you did not!’
‘– I meant to, and that’s what did it. I’ve done what my mother did. They’re protected from you. Haven’t you noticed how none of the spells you put on them are binding? You can’t torture them. You can’t touch them.”
- Harry Potter and the Deathly Hallows, Chapter 36 (The Flaw in the Plan)
Ingen ytterligare magi behövdes för att tillåta ett avsiktligt offer för att skydda personen den har gjort för.
Dumbledores charm var bara för att skydda Harry vid Dursleys.
Vad Dumbledore gjorde var att skapa en charm som säkerställer att Harry var skyddad vid Dursleys. Lily's offer inträffade före det, och Dumbledore behövde inte "aktivera" hela offerets skydd - han gjorde bara den del som skyddade Harry vid Dursleys.
“For he has been better protected than I think even he knows, protected in ways devised by Dumbledore long ago, when it fell to him to arrange the boy’s future. Dumbledore invoked an ancient magic, to ensure the boy’s protection as long as he is in his relations’ care.”
- Harry Potter and the Goblet of Fire, Chapter 33 (The Death Eaters)
Dumbledores charm använde helt enkelt Lilys offer, som redan hade hänt och lämnade effekten på Harry, så att Harry skulle kunna skyddas vid Dursleys hus. Dumbledore förklarar detta till Harry - Lily gav Harry ett långvarigt skydd genom att dö för att rädda honom. Därför valde Dumbledore att använda den charm som skyddade honom vid Dursleys hus.
Effekten av Lily's offer existerade innan Dumbledore använde det för att skapa sin charm - det är därför han valde att använda den specifika charmen för att skydda Harry.“You would be protected by an ancient magic of which he knows, which he despises, and which he has always, therefore, underestimated – to his cost. I am speaking, of course, of the fact that your mother died to save you. She gave you a lingering protection he never expected, a protection that flows in your veins to this day. I put my trust, therefore, in your mother’s blood. I delivered you to her sister, her only remaining relative.’
‘She doesn’t love me,’ said Harry at once. ‘She doesn’t give a damn –’
‘But she took you,’ Dumbledore cut across him. ‘She may have taken you grudgingly, furiously, unwillingly, bitterly, yet still she took you, and in doing so, she sealed the charm I placed upon you. Your mother’s sacrifice made the bond of blood the strongest shield I could give you.”
- Harry Potter and the Order of the Phoenix, Chapter 37 (The Lost Prophecy)