The third adversary is the devil and his demons. This is an enemy with thousands of years experience, therefore making thim and his army all the more challenging. St. Paul identified this enemy:
“For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places.”
--St. Paul of Tarsus
It is important to point out that he is in no way saying that we are not warring with our own flesh. In this passage he is stating that this war is not against a person or an army of people.
“So the evil one likes to be served by things that appear good. He is versatile and cunning in the lust of the world.”
--St. Macarius the Great
In the book called The Arena, written by a Russian mystic from the 19th century, St. Ignatius Brianchaninov, warns that when we take up battle against these three enemies all will quickly escalate:
“If you deny yourself and constantly renounce your own opinions, your own will, your own righteousness, or what amounts to the same thing, the knowledge, understanding, will and righteousness of fall in nature, in order to plant within you the knowledge of God, the will of God, and the righteousness of God taught us in the Holy gospel by God himself, then Fallen nature Will Open Fire Within you and declare a Savage war against the gospel and against God. Fallen spirits will come to the help of Fallen nature.”
--St. Ignatius Brianchaninov
So why would God allow us to be attached and influenced by the Devil and his army of fallen spirits? The answer can be found in the writing of St. Maximus the Confessor:
"There are said to be five reasons why God allows us to be assailed by demons. The first is so that, by attacking and counterattacking, we should learn to discriminate between virtue and vice. The second is so that, having acquired virtue through conflict and toil, we should keep it secure and immutable. The third is so that, when making progress in virtue, we should not become haughty but learn humility. The fourth is so that, having gained some experience of evil, we should ‘hate it with perfect hatred’ (cf. Ps. 139:22). The fifth and most important is so that, having achieved dispassion, we should forget neither our own weakness nor the power of Him who has helped us.”
--St. Maximus the Confessor
We won’t speak much here about the devil and the demons, as there can be a temptation to blame all our faults on them as a means of deferring our own accountability and responsibility.
These enemies may seem as ginormous Krakens or Godzillas that are unconquerable. But know that they can be brought down to submission and even death. In conclusion it is fitting to lean on the words in The Ladder of Divine Ascent: