Dark Legacy

Dark Legacy is a tool which was created and discarded by Heaven Canceller at some point in his past that Academy City started using, likely without his knowledge.

Principles
Dark Legacy is able to rapidly rebuild the human body no matter how badly it is damaged by using an oil-based melted framework to adjust the regeneration pace of the flesh, bringing about high-speed cell division and keeping the brain alive.

DRAGON Arc
When Mugino Shizuri meets Hamazura Shiage again she mentions that Academy City used Dark Legacy to save her life, preventing her from dying from the injuries sustained during her fight with him. Mugino also later comments that Dark Legacy was also used to preserve the Dark Matter ability of the #2 Level 5 esper Kakine Teitoku by keeping his brain and organs alive.