All the things that others have mentioned (particularly the Rawr! Hotness!)
But the level of symbolism - the aptness of the characters' associations, ManannĂ¡n's triskele on Severus'/Nuada's shield and cloak pin, in addition to the Hp allusions!
I'm in awe!
Might you possibly consider writing the story as well? And/or, as noted above, doing the whole Mabinogion?