enkephalin (project moon)

A green substance from the Project Moon series that is used as an energy source.
In Lobotomy Corporation, it is the manager's job to extract it from interaction with abnormalities.
In Limbus Company, Mephistopheles' engine can synthetize it from corpses, with the brain being the most efficient organ for this process.

In real life, this substance is an opioid, which is reflected in the series by having it be an addictive substance that quells pain.