Cain = first born of Adam; foreshadowing those who pervert the pure gospel message of salvation through Jesus Christ and receiving His Righteousness by faith, for a salvation based on man’s dogmas/opinions and works; followers of Cain receive a mark and are cursed (Genesis 4:3-15; Galatians 1:6-9; Rev 13:16; 14:9 11; 1 John 3:12)
So... what's the mark of Cain?
A curse that the serpent seed Cain received for murdering Adam's true son, Abel.
https://www.youtube.com/watch?v=SoUkkcDDNT8