Unbeknownst to the departing Shinigami and even to most of the Arrancar in the room, there was another who had been watching the meeting unfold with no small amount of interest.  An Arrancar known by few and trusted by even fewer.  He stood silently with his back to a wall away from the gathering, his arms crossed sternly over his chest and shadows partially hiding him from obvious sight.  He also kept the presence of his reishi mostly hidden, although more out of an act of polite courtesy rather than for spying.<br/><br/>His name was Dietor Ziesel.  And he was the deadliest and most skilled assassin Hueco Mundo had ever seen.<br/><br/>If the Ten Espada were seen as Aizen's ten swords, then Dietor Ziesel was the cloaked dagger.  The invisible blade that killed from behind rather than fought from the front.  He was the executioner of treasonous Arrancar, the silent enforcer of the laws governing Las Noches, and Aizen's secret weapon against those who would dare to usurp him.<br/><br/>But in the eyes of the Espada, Dietor was simply nothing more than Ulquiorra Schiffer's rarely seen FracciÃ³n.  Only Ulquiorra himself knew of Dietor's true role in Las Noches.<br/><br/>A narrowing of green eyes was the only sign he gave as the Shinigami vanished into the Garganta.  He was clad in the attire of the Arrancar that consisted of white shihakushou leggings, a matching long jacket hanging just below his hips with the collar upturned, black gloves with the fingers missing, and black boots typical to almost every Arrancar.  A black longsleeved shirt that fit snugly beneath the jacket completed the ensemble.  His tousled hair was short and black and the remnant of a Hollow Mask completely covered the lower half of his face.  It was little more than a plain facemask similar to a shinobi's in shape, but with a simple pattern of embossed fangs designed to make it resemble the open mouth of a snarling beast.<br/><br/>As the Garganta finally closed and sealed the void between Seireitei and Las Noches, Dietor flickered his gaze between Aizen and Kaname Tousen.  He knew better than to try and fathom the minds of those two men, but the idea of simply releasing the Shinigami like that had even stirred his curiosity.  And Dietor was almost<i>never</i>motivated enough to feel that particular emotion, being the cerebral and content soldier that he was.<br/><br/>But even so, Dietor guessed that the reason why Aizen had specifically requested Ulquiorra to bring his "unofficial FracciÃ³n" along to this meeting had something to do with this moment right here.  And until either Aizen or Ulquiorra saw reason to acknowledge his presence here in front of the others, Dietor would remain silent and unseen as he had always done.  It was simply his way.  It was better to let others wonder if you're a fool rather than to open your mouth and prove them right.