I too was surprised to see that apparently, not one Slytherin remained... except that I think Slughorn helped in the defense of Hogwarts, didn't he? He's the only one that comes to mind... isn't there a sentence about him leading a group of the defenders? And I guess one could argue that Malfoy contributed, although unintentionally. And Crabbe or Goyle conjured the fiendfyre that destroyed the diadem. So I guess, except for Slughorn, the Slytherins helped only by accident.
Or perhaps Narcissa counts? After all, she did lie to save Harry and though it isn't mentioned, you've got to think she was in Slytherin.
I too was surprised to see that apparently, not one Slytherin remained... except that I think Slughorn helped in the defense of Hogwarts, didn't he? He's the only one that comes to mind... isn't there a sentence about him leading a group of the defenders? And I guess one could argue that Malfoy contributed, although unintentionally. And Crabbe or Goyle conjured the fiendfyre that destroyed the diadem. So I guess, except for Slughorn, the Slytherins helped only by accident.
Don't forget the guy that basically put himself through hell his entire life to work against Dumbledore: Snape