What if...?
"So how much further to the capital?" Joshua asked.
"Well, it will be a couple more hours, but it will be soon." Lucy said.
"Teach me something useful then." Joshua instructed. "I still have an extremely limited variety of spells in my arsenal, what kind of demon lord is low in spells? The spells I do know are world ending, well most of them are."
"I don't think it is wise to teach you any more magic." Lucy said. "A simple fireball from you might end all life as we know it or destroy a planet if you launched it into space. It is not something that we should take lightly. I do not feel safe teaching you anymore attack spells."
"Doesn't have to be an attack spell." Joshua said. "You taught me Scan, which was useful and cool. Surely you know more spells like that, what about your void storage?"