The Devil is the card of bondage, whether that bondage be to an addiction or unhealthy pattern, or to a habit of attention or way of looking at the world.
We see the world, not as it is, but as we are. In other words, our habits of attention, our neural pathways, determine, to a large extent, how we experience our lives and the world around us.
St. Paul has some advice on how to beat the Devil, in his letter to the Church at Rome.
Be not conformed to this world, but be ye transformed by the renewing of your mind.
When we change our minds, we change our reality.
The Devil card turns up as a reminder that we can break the chains that bind ourselves to a world of illusion. We see past fear, and begin to look at the world with love.