He set out for the Moon Nexus

After long thinking, Callum decided that there was no better place to begin his new quest for knowledge than one he had already visited: the Moon Nexus.
He loaded his things on the new horse Ezram had gifted him, Jackass, gave the last farewell to the Queen and Zym and then set out.
Technically, the Moon Nexus wasn’t inside of Xadia’s border anymore since centuries, it was Katolis’s, so he wouldn’t even have needed the Dragon Queen permission to visit it, yet Callum had come to believe that he had already came close to learning the Moon Arcanum once there.
All he needed to do, was to pick up where he had left.

Also, going back to Silvergrove, the only other place with strong Moon connection that he knew of, wasn’t an option in Callum’s mind. He suspected that very few of the villagers would welcome with joy his desire to defile their centuries-old traditions, especially after having done the same to one of their most promising children.
While Ethari would probably be still on his side, he couldn’t really imagine anyone else in the village willing to help him out in wrecking another long established custom, that humans must not meddle with magic.
Besides, going there could mean meeting Rayla, and Callum wasn’t sure he wanted to see her. Yet.

So the young mage had resolved that the old nutty Lujanne was his best bet.
She had gave him some pretty illuminating advices in thepast, but he hadn’t been able to completely understand the meaning of her words.
Now he was a different person, he was a man, he knew he was capable of learning a Primal, and that gave him confidence and purpose.