A symbol in alchemy of the sacred fire or Kundalini.
"Sulfur is the fire of Alchemy." - Samael Aun Weor, Treatise of Sexual Alchemy
Since we have lust, pride, envy, etc., that fire is modified, and is called Arsenic (i.e poisonous) Sulfur.
“Whosoever awakens the consciousness stops dreaming. Whosoever awakens the consciousness becomes a competent investigator of the superior worlds.”
Samael Aun Weor, Dream Yoga