This...is not independent of the Harry Potter series, but the connections are connections Kaiya created, that are surprisingly appropriate to who the Dark Mongrel truly is. The Dark Mongrel is real, at least to me.
Consider the meanings of dark...complexion, magic, names--for the Basilisk Cur only, anti-heros, and, of course, the color black.
Think about mongrel...something that isn't pure, but a mixture of things, that may not be respected for its lack of purity but is stronger for it.