"That's a good bit of learning on the fly when it comes to advanced magic," Neville soothed. "And you aren't entirely wrong, either. I think there are some animals that a wizard finds it easier to invoke, based on their own personality. Harry, for example, is obviously very much a lion in so many ways that the list is extensive, from alchemy to astrology to his own fierce nature. When he summoned the lion spirit to infuse him, it came to him as if it was Harry's right to call it. Not everyone is so fortunate, and a wizard can always pick a different animal of his choice, despite any natural affinity, but then he has to commit to a tougher process to invoke it fully."