The house-elves will not appear again. The trio's mission is full of despair: Although they can kill a few evildoers, they have no hope of fixing the evils of their society.

In the bubble at the top, I knew I wanted the elves' training to be overseen by one of the founders, but it took me a while to decide who it should be. I sketched in Slytherin at first, but ze seemed too obvious. Plus, I'd expect the actual Salazar Slytherin to be more of a “hands-off” person – someone who wants to profit from this dirty business, but not actually be involved in it. Between Ravenclaw and Gryffindor, I settled on Gryffindor for two reasons:

1. I wanted to play up the “Gryffindor may seem like a good guy, but ze's not” idea from the previous page.
2. With the sword and the boots, I'm going for a fighter/conquerer image, and that fits perfectly with the subjugation of another race.

That said, there was a point in Ravenclaw's favor, too. Using Ravenclaw would enhance the “Ze thought about the elves' lives purely as a logistical problem” angle.

As a side note, I've recently learned that in J.K. Rowling's vision, Helga Hufflepuff brought the elves to Hogwarts. In that version, ze did it because no one would be cruel to them in the Hogwarts kitchens, which was the best ze could achieve in an era of history when nobody would accept actually freeing them. I think there's some merit to that version of the story, but it fits much too easily into the books' narrative of Harry's and Hermione's interactions with the elves (especially Kreacher), where the moral of the story seems to be “It's okay to have slaves, but you should treat your slaves nicely”.