Kirei cast his eyes to a corner of the darkness when he heard a painful moan. The Einsbern homunculus that he had gotten Berserker to kidnap was lying there face-up. She wasn’t lying there naturally; a simple Magic Circle had been drawn around her to allow the surrounding prana to flow in. Although this location was not above a leyline, there was still leftover prana gathered here from when Caster had greedily devoured the souls of those he had sacrificed. Putting aside whether this supply made her comfortable, it was enough to stabilize her condition.

Of course, it would have been easy if he were to simply cut open her abdomen now and take out the ‘Vessel of the Grail’. However, Kirei wished for a chance to speak with her. That was why he was wasting his effort to provide her with prana.

- Fate/Zero: Act 15, Part 3