I see you have him trying to manipulate mist. Is it actual mist or the mist monsters create? Manipulation of the monster mist is an ability that almost all demigods can learn with practice. It allows them to mask mortal eyes to what they are really seeing. Only a few characters do it in the books, but it seems implied that others can do it as well. Even if not, the girl that did it in the book was a daughter of Zeus, so if it's a family trait then Desmond would be able to learn it too.