When forging the Leviathan Shadow Ego Eternal Technique, Cain aimed to create a weapon that would grant its bearer devouring power capable of improving their strength and cultivation. Since the ethereal snake was an embodiment of willpower, Cain saw no reason for it to be bound solely to the physical plane. His goal was for the snake to feed not only on life force and energy but also on emotions, similar to how the Depravita Race sustained themselves.
Cain's willpower and Ego Wave had been nurtured with the essence of the Depravita Race in many ways—by consuming the Depravitas that attempted to invade Aether and absorbing the Depravita Essence that the Demon King expelled during his evolution. Cain had fused the power of the Concept of Gluttony and the Concept of Rage into the Leviathan Shadow, hoping they would achieve the synergy needed for the entity to consume emotions. And it was a success!