Demon core, a spherical subcritical mass of plutonium manufactured during World War II by the United States as a fissile core for an early atomic bomb

a demon

A transliteration of the English male given name Damon

(computing) a daemon (a background process running on a computer; often specific to such processes running on Unix or Unix-like operating systems)

dangerous; risky

danger

(engineering, computing) core / (only in compounds) core (being central, crucial)

(slang) hardcore, passionate

extraordinary, unusual

emergency