Guren

is a kunoichi who appears in the second Naruto Shippūden filler arc. Little is known about her yet. She is seen using what she calls and also seems to be a companion of Orochimaru.

Hunt for the Three-Tails Arc
To aid him in final preparations for his plan, Orochimaru sent Kabuto to fetch Guren (much to Kabuto's disapproval). Upon approaching her domain, Guren attacked Kabuto with a barrage of her deadly crystal release jutsu. Kabuto manages to evade all of her attacks and accuses her of knowing all along who he was. Guren smugly states she just wanted to make sure Kabuto was worthy of being Orochimaru's right-hand man. Upon returning to Orochimaru's current hideout, she was put in charge of having hundreds of test subject prisoners battle each other to the death.

Personality
Guren has shown to be a very mysterious konoichi, apparently preferring to keep to herself despite have a strong loyalty to Orochimaru. Her loyalty is not unlike that of Kimimaro as she too was at one point a willing canditate to become Orochimaru's next body. During her introduction, she quickly showed herself to be a remorseless and sadistic person. When told by Kabuto that several prisoners would be fighting to the death, she became ecstatic to here there would be a slaughter.

Abilities
Guren possesses a unique ninja art; the Crystal Release. It is unknown if this is a unique kekkai genkai or secret technique. By using this power, Guren can summon and manipulate crystal in a number of manners such as creating crushing walls or unique shuriken. This ability is presumed very powerful as Orochimaru at one point desired it for himself.

Trivia

 * There have been arguments as to if Guren's Crystal Release is a sub-element similar to Haku's Ice Release and the First Hokage's Wood Release.