Kill and you’ll be killed.
Take life and you owe a debt of blood. The victim will not be satisfied until you pay for their sufferings.
This karmic debt is stored in our 8th consciousness until it is resolved.
This is why there are mortal enemies, e.g. in the human realm such as suicide bombers. On the surface, these people may seem to be motivated by some so-called heavenly rewards (such as heavenly maidens), but at a deeper level, there is a blood debt settlement between these groups of people.