And Quirrell, though pinning Harry to the ground with his knees, let go of his neck and stared, bewildered, at his own palms – Harry could see they looked burnt, raw, red and shiny

Your mother died to save you. If there is one thing Voldemort cannot understand, it is love. He didn’t realise 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 for ever. It is in your very skin. Quirrell, full of hatred, greed and ambition, sharing his soul with Voldemort, could not touch you for this reason. It was agony to touch a person marked by something so good.

So. Your mother died to save you. Yes, that’s a powerful counter charm.

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.

His mother left upon him the traces other sacrifice. . . . This is old magic, I should have remembered it, I was foolish to overlook it... but no matter. I can touch him now

I miscalculated, my friends, I admit it. My curse was deflected by the woman's foolish sacrifice, and it rebounded upon myself

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. Not even I can touch him there. . . .

But I knew too where Voldemort was weak. And so I made my decision. 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 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.

While you can still call home the place where your mother’s blood dwells, there you cannot be touched or harmed by Voldemort. He shed her blood, but it lives on in you and her sister. Her blood became your refuge. You need return there only once a year, but as long as you can still call it home, there he cannot hurt you. Your aunt knows this. I explained what I had done in the letter I left, with you, on her doorstep. She knows that allowing you houseroom may well have kept you alive for the past fifteen years.

“Now, your mother’s charm will only break under two conditions: when you come of age, or” – Moody gestured around the pristine kitchen – “you no longer call this place home. You and your aunt and uncle are going your separate ways tonight, in the full understanding that you’re never going to live together again, correct?

He took your blood and rebuilt his living body with it! Your blood in his veins, Harry, Lily’s protection inside both of you! He thethered you to life while he lives!