Because of his fiery nature, the lion is the ‘affective animal’ par excellence. The drinking of the blood, the essence of the lion, is therefore like assimilating one’s own affects.
Jung defines the lion as the archetypal embodiment of uncontrolled affect, and proposes that the alchemical act of drinking the lion’s blood symbolises the psychological integration of one’s own passionate emotionality through insight.
, Mysterium Coniunctionis: An Inquiry into the Separation and Synthesis of Psychic Opposites in Alchemy, 1955thesis