Archetypes in the Tarot: Shadow
Carl Jung's archetype of the Shadow represents all the aspects of the human nature that we devalue. Hatred, greed, wrath, selfishness, excessive lust, and jealousy are all examples of the behaviors attributed to the Shadow.
In a tarot reading, the Shadow appears to show us someone who is not acting with their better self, but rather with a negative intent and effect. It is often a warning, because when dealing with a person acting as the Shadow things are often not as they seem and caution is advisable.