A Key Called Promise

Slytherin has been lumbered with a disagreeable, low-class, shouty, raggedy bat-troll. With a most unreliable sense of self-preservation. Ick. And he's even half *muggle.* Or maybe just half mother-hen... But either way, noisy, and trouble, and... an excellent decoy, come to think of it... and what do you mean the only Black the little mudblood hasn't scooped up is the Gryff?