Snape, a Deatheater who assists suicide?.

[zgirnius]

No: HPFGUIDX 164059

Nikkalmati:
> Are you saying the potion in the cave was poisonous and DD drank it 
because  
> he knew he was already dying, so that if it actually was the potion 
that 
> killed  him, it was not Harry's fault?  I would find it hard to 
believe DD would  
> take poison just to procure a Horcrux when there were so many 
others yet to be  
> found and even less would he make Harry feed him poison - - - 
unless he 
> thought  for sure that Snape could save him.

zgirnius:
Ah, but then there is the Vow. Perhaps Dumbledore was confident that 
Snape could save him, in the sense that he had the skills and know-
how to provide an antidote if Dumbledore got himself to Snape before 
the potion finished him off. This could be why Dumbledore's first 
thoughts upon returning to Hogsemade were to get Snape.

However, the Dark Mark over the castle took precedence in Dubledore's 
mind over his own health and well-being, because it meant that his 
students might be in danger. And when Snape finally showed up, he 
literally could not save Dumbledore: the third clause of the Vow was 
in play, and an attempt by Snape to save Dumbledore rather than kill 
him would have caused Snape's own death by the Vow. (I presume saving 
Dumbledore is not something Snape could do in an instant).