Alright. So, we clearly could tell that Husk and Alastor have a past together, especially from the scene in the first episode of the Pilot, when Husk and Alastor meet again. I have noticed that some people haven't noticed the part in Vaggie explaining who Alastor is to Angel Dust, there is a frame where a familiar figure can be seen:

Look behind Vaggie on the left. We can see a wing, a hat, ears, and a hand, all of them look like features that Husk has. So, what else is going on in this frame?
Well, Alastor doesn't really appear to be doing anything too wrong. In fact, he looks like he is laughing, possibly having fun? We can't see what (I think) Husk is doing, but it is a possibility he could be laughing or enjoying himself too. What else do we know?
When Alastor and Husk see each other, Alastor calls him Husker, when his name is actually Husk. Husker seems to be a nickname for Husk, and he gave Alastor permission to call him that at some point, at one point they were friends.
But how..?

That's what I'm trying to put together at the moment, I'll update this when I come up with something