Ulquiorra opened his eyes, his gaze flickering to Zexion, but he didn't interrupt. When Zexion finished, Ulquiorra intoned, his voice deep, and low, "We will be observing from outside. Any aggressive spikes in reiatsu, and we will intervene."

Uninvited. Ulquiorra didn't expect that Zexion was going to get aggressive, but there was the possibility that Vexen would once confronted with Marluxia, or that Marluxia would if he considered the moment without the Arrancar presence to be an opportune one. Ulquiorra wasn't here for Marluxia's safety, but he didn't trust him any further than he trusted Gin, and Vexen was an unknown quantity.