"Dragon Ninja" (竜の忍者 Ryū no Ninja) is a sub-series of the "Ninja" archetype.
Despite being "Ninja" monsters, members of this series are not the traditional Warriors. Instead, they each are of a different Type that would allow them to be Special Summoned by "Ninjitsu Art of Transformation" or "Ninjitsu Art of Super-Transformation".
All members of this series are based on their masked counterparts (known as "[Color] Ninja" in Japanese), and each appears to wield a different golden-colored Japanese weapon.
All cards are centered around disrupting the opponent's strategies and overall effectiveness. "White Dragon Ninja" prevents your Spell/Trap cards from being destroyed, "Red Dragon Ninja" returns Set cards back to the top of your opponent's Deck, "Blue Dragon Ninja" stops monsters from attacking or using their effects, "Black Dragon Ninja" banishes opposing monsters, and "Yellow Dragon Ninja" destroys Spells/Traps.