Euphemism for Semen, cum, jizz, ejaculate, spunk, scum, baby batter, etc.
If you're in bad mood and jerk off. You feel better. Because
the "Liquid Evil" is out of you.
If you're receiving
felatio, and you ejaculate on to the girl's (or guy's) face without warning. They get angry, because
they got "Liquid Evil" on them.