The spell casted by Raul was not a forbidden spell. Athy knew that something like this could happen so, she changed all the spells beforehand.
Now with Raul dead, the violent gore stopped and eerie silence prevailed. All the vampires looked at the one they were following. Now without any leader to follow, they has lost their goal.
Whereas, when they turned to Cassie, she was in no shape to lead anyone, she has become violent and has killed many from their clan.
Now another thought stopped in each of their mind – who will be the next leader?
This unfolded differently. Pure blooded vampires separated and formed their own groups and started to have a fight within their own group to decide a leader, foolishly ignoring that there were still wolves, though low in quantity but with how things were going, they will surely kill each and every vampire.