At the moment, it exhausts him fairly quickly; even a simple spell makes him feel like he just ran a mile, but he also recovers at a fairly steady rate. A few minutes rest, and he'll feel almost as good as new.<br/><br/>It's easy to lose track of time in an underground city; he'll hardly notice it's close to dinner time until Sapphire returns, to watch the two of them practicing. "He's getting pretty good with that," she says.