As I suggested earlier, with the part about Ignatius, Percy might have
to suffer an injury in battle before he changes his mind about his
family, Harry, and anyone else who supports Albus Dumbledore's cause.
This would be the begining of his "conversion".
Perhaps to show he has changed he will have to perform some great
deed, defeat someone or something that would allude to Medusa. Who
would fit the concept of the Medusa? Maybe Bellatrix Lestrange? She
was a beautiful woman before her arrest, but Azkaban has taken away
much of her beauty... and possibly what was left of her sanity! Maybe,
but I'm not sure. The only being I can think of that goes through a
drastic change, from beautiful to hideous (and back again), is a
Veela....
I'll talk about Percival later....