Rook explains that his unique magic I See You (hidden meaning: The bow and arrow that reaches the very end) cannot hurt anyone or control anything, but is essential for a hunter like himself.
He says it can locate anyone upon whom it is cast, but we later learn that he can also cast it upon objects.
Rook struggles with his unique magic in Book 6 after casting it someone who is on board a technomantic stealth aircraft that can block magic.
But, he explains, “not even a technomantic plane can completely block out magic. They must drop stealth for the briefest of moments when using magic or radar. And in those precious seconds, I can envision the mark I’ve put on my prey.”
Re-casting the spell, Rook succeeds in tracking his target.
Rook explains, “The spell isn’t aggressive and contains no toxicity. It appears to have no point and no effect at first glance.”
Epel responds, “that spell’s even scarier than I thought…If he put his mark on someone, they wouldn’t even know it was there, would they?”
In addition to using his unique magic on a member of CHARON (in order to follow Vil) Rook also casts it on a skin care product to locate Vil, and he uses it to track Vil in his dream of Book 7 as Vil is dragged into darkness.
Twisted Wonderland Reference Note 