Medusa. Lucifer had some knowledge of her experiments, but never in great detail. He certainly hadn't had any idea that Medusa had experimented on her team mates. If she was still here, they would have had things to discuss. He wondered if Yako was the only one.
"Black blood," he replied, somewhere between a statement and a question. He had no more than heard the name prior to then, but it seemed a fitting enough description. If that was it, then it was a safe bet that the power was tied to her blood. In which case... he muttered something incoherent and hoped it had the expected effect on the substance ripping at the room--namely, to attract it back to the way it would normally be stored in her body. If it worked right, it would be a somewhat painful process for her, but shouldn't cause any lasting damage.