Jinni

Why is our boy Julian getting chased across A FREAKING DESERT by FREAKING BIRD DEMONS???!!!

When Kit told Ty that he would help Ty but not if he did this(necromancy), he did not ask Ty to choose between just Kit and Livvy. He already knew that when it came to that, Ty would pick Livvy. Instead, he asked Ty to choose between the ones alive, his family, the people who loved him(including Kit), those who were still there for him and destroying himself and his loved ones (mentally/emotionally) by committing necromancy.

It was just that Kit's timing, his panic and the situation as a whole prevented him from phrasing this properly.

So when Kit says that he is mad at Ty for changing himself from the one he loved, he meant the Ty who would think about his whole family before doing something. The Ty who would rationally think things through all perspectives being making any decisions. The Ty who was ready to hear him out. The Ty who wasn't ready to sacrifice his own mental wellbeing and raise his sister from the dead, no matter the cost.

Besides we already know The Wicked Powers is based on Arthurian Legends.