Those who enter into the difficult path of liberation from the causes of suffering need help from divinity. The compassion of the divine sends unto the deserving the fierce intelligence that wages war against the selfish, impure, lustful, etc. Amongst the many religions, that great warrior god has many names: Ares, Mars, Samael, סמאל, Kartikeya, etc. The 27th of October is a celebration of how this force can aid us in our battle against ourselves.
The energy of Ares is generally used by humanity only for violence and warfare against others. Yet like all energies in the universe, this force can be harnessed for good by those who awaken consciousness through eliminating the psychological defects we have within: pride, anger, lust, envy, etc. This contrast between external battles for the ego and internal battles against the ego explains the diverse interpretations of the stories of Ares, Mars, Samael. How we relate this energy and use it is up to us.
The Advent of Samael is celebrated on October 27th due to its Kabbalistic, astrological, and numerological significance.