Ancient Magic vs. Dark Magic (was ancient magic)

[corinthum]

No: HPFGUIDX 82047

Jen:
  
> We see many everyday spells that consist of one person casting a 
> spell directed at an object or a person, and we see a specific result 
> (or not). But then we're presented with a few, a very few, examples 
> of magic that create a *bond* between two people. It's a much deeper 
> form of magic than two people casting spells at each other.

I see it as the opposite: the bond comes first, and creates a magical
result.  In both the Lily-sacrifice case and the Harry-saves-Peter
case, the creation of a magical bond was not the intention of the
action, but an unplanned side effect.

> The life debt and blood sacrifice are two such examples. You 
> disagreed that the secret keeper is ancient, but I included it 
> because it forms a bond between two people that could require a life 
> sacrifice on the part of the keeper. 

The charm itself doesn't require anything of the secret keeper.  It
would be nice if he or she didn't go blabbing to the next person he or
she met, but there isn't anything stopping that.  If the Secret Keeper
were to give his or her life to keep the secret, that might result in
a magical-bond-ancient-magic scenario.

Me:
 
> > Again, there is no indication that [the Fidelius] charm is
ancient.  Nor does 
> > it necessarily require Lily's sacrifice.  It is simply a charm that 
> > gives protection to a person when said person is in the home of a 
> > blood relative.  Also, it is unlikely that the spell is based on 
> > emotion; Petunia shows no sign of loving Harry.

> Jen:
  
> In OOTP, Dumbledore explains that the blood sacrifice Lily made is 
> only activated when Harry "calls home the place where your mother's 
> blood dwells."  So Lily's sacrifice would be meaningless if Petunia 
> didn't allow Harry to dwell in her home. Petunia's choice completes 
> the circle of magic begun when Lily died.

I interpreted his words differently. 

"'...I put my trust, therefore, in your mother's blood....  [Petunia]
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.'" (OoP, US p 836)

>From this, I took it to mean the mysterious charm Dumbledore used was
strengthened due to Lily's sacrifice.  Therefore, Dumbledore's charm
would be useless (or at least less powerful) without Lily's sacrifice,
but Lily's sacrifice does not rely on the charm.  This is simply one
way the ancient magic effects can be harnessed.

-Corinth