What is considered the Dark Ninja Arts? As we all know the ninja uses trickery as much as he/she can to win a fight. To loose means death. There are no other options than to win. But there is an honor to the fight/battle and to winning, and to do so using the utmost deceitful trickery is considered a dishonor.
Many may think, "So what? I would do what I can just to win if it meant living." True. But to call on the dark forces to do your bidding is not honorable. Think of it as cheating during a game or competition. If you win and get the trophy under deceitful terms was it really winning?
Duncan Kimura and his team face such foes in further books of the Shadow Legacy series. They share inner struggles with what is right and wrong, honorable and dishonorable, during a battle. "But they're ninja!" you say. Yes, but there is deep honor in the ninja way. Think about it....