So why did Severus Snape agree to the Unbreakable Vow anyway?
I've seen some people bringing up this question. Because would Snape's Unbreakable Vow to Narcissa not necessarily cause great difficulties for him IF he's really on the good side? Since he makes this vow, doesn't this automatically mean that he's not on the good side?
Thought about this for awhile and here are my ideas:
- Snape doesn't have much chance to not make this vow to Narcissa. Bellatrix is convinced he's a traitor. That he takes the vow obviously is a big surprise to her. It seems that for the first time she doubts her judgement that Snape is double crossing the Dark Lord.
- Snape hesitates at Narcissa's third request, namely that he carry out Draco's orders if he fails. Quite possible that he did not expect Narcissa to go this far. Of course, he can't back out at this point.
- And the most important reason, IMO: Snape *wants* to take the vow. He *wants* to protect Draco.
All these years he has protected Harry, a boy he strongly dislikes because he reminds him too much of James.
Now he's given the chance to protect Draco, a boy he appears to like. (I don't think any student could just burst into his office and not be severly reprimanded. Snape tolerates this sort of behaviour from Draco in book V. He even calls him "Draco", every other student he always calls by their last name.)
I also think that he identifies with Draco quite a bit. In some ways, he must have been like him when he was that age. While he always got defeated by James and his friends, Draco's nemesis is Harry. And like Draco he probably tried to prove himself worthy of the Dark Lord when he was young - not knowing what sort of deal he was entering.
So when he gets the chance to tie his fate to Draco's, he takes it.
If he hadn't, he always might have been worried that one day he would have to make a choice and in the course of this choice he would have to risk Draco's life. By making the vow, he's got a very good argument on why he *has* to keep Draco safe.