The lower carnal mind, the left hemisphere that tills its own soil, is not to be killed but marked and preserved. Cain carries a sign that keeps him alive because the earth-nature in a person is never meant to be destroyed. It is meant to be subordinated, subjected to the spirit and led rather than slain, the servant kept on so the higher mind has ground to stand upon.
The sevenfold vengeance names the price paid all the way up the spine. The number 7 is the 7 chakras, the 7 nerve centers along the column from base to crown, so an assault on the lower self reverberates through every one of them. Whoever tries to cut off the earth-mind at its root disturbs the whole ladder of energy that rises through the body. So the lower mind lives on under its mark, subject to spirit, carried and not erased.
Cain: the left hemisphere, the lower carnal mind that grows ideas from its own ground and must be led, not killed
Mark: the sign of preservation set on the earth-nature so it is subordinated rather than destroyed
Sevenfold: the 7 chakras up the spine, the toll paid through every nerve center when the lower self is struck