It didn't make any sense????
Spoilers
I rated this one lower because too many things were over-dramatized and made no sense.
First of all, it annoyed me how they were being all over the top about her using "dark magic" on the outsider alpha. All she did was make him walk to the cauldron. Even then all she was going to do was take a freaking drop of his blood. She was NOT marching him off to his death, she was NOT about to sacrifice him, she was NOT about to make him harm anyone else. There's absolutely no reason magic should've started to corrupt her and turn her skin black and gray, that's stupid. She didn't do anything to warrant that at all.
Adding to those facts, it was discovered that the alpha was just going to basically bleed the remaining energy in their pack lands dry. Then he was going to leave their pack to rot after he stole all of the power to help his own pack. So one measly drop of blood was more than even in the balance of the price he should pay for what he tried to do to all of those people.
Then one of the elder showed talking about some "this is not the way." That's not an elder or guardian I would ever want to have. It's like "YES, he was about to take all the land's magic and wipe out the entire pack, but no, you forcing him to give A DROP OF BLOOD is going too far."
It's a major plot disturbance that made no sense to do. If the magic had gotten a hold of her and she slipped into the dark and was actually trying to outright murder the alpha and his pack then yeah, darkness should be spreading or whatever. But that was NOT the case. Especially when he soad out of his own mouth that the reason he wasn't going give them any of his blood was because he wanted to use their pack to benefit his own and then hand them out to dry.
Taking a drop of the alpha's blood was apparently worse than that same alpha consigning their entire pack to death??? That makes no sense. The book was good up until the last couple of chapters where that happened. It made absolutely no sense. Maybe even if there was just a SMALL SPOT of darkness on her skin AFTER taking his blood, that would have been acceptable. Since technically she would have drawn blood while doing a *very light tier* dark magic spell. But for her to start to be visibly corrupted on a large scale before she even did anything is ridiculous.
I'm sure it was added in for drama or some type of plot twist, but it didn't make any sense in the situation. I'm going to continue the series because I was enjoying it before that happened. But hopefully nothing like that is forced in the next book.