Believe?

Leonel appeared in the far off distance with a pale expression. It looked as though his face had been completely drained of all color. 

Using this ability really took a lot out of him, though, he could already see some of its parameters. 

When he used it on actual people, the requirements were far more stringent. He also noticed that the closer something was to being "complete", the more difficult it was as well. 

Take, for example, the arrow that the demon monkey sent his way. Because it was close to taking his head, and he waited so long to say the words "disperse", it took more energy to deal with it. 

If he had commanded as the demon monkey was taking action, or before it had taken action, he would have been in a much better situation. This was his measure of "completeness". 

So why was he so tired now? Was it because he had used it on himself, or Little Blackstar, maybe?