Execution, How Does it Happen?

Nightmare is a celestial cosmic being of comlpete and utter destruction, he was caputred and imprisoned in the kage office back in the nightmare village. He goes around claiming the souls of those who I choose, and he is how every prsioner will die. When prisoners leave thier cells, they will have the after affect of the cell that they are in for the rest of their time in the prison, The S.T.A.L.K.E.R.S and I would then summon nightmare who will then summon his trademark sword, soul edge. Sould Edge has the power to kill the target, it sounds pretty simple right? WRONG! Soul Edge is a mythical blade that kills the target once they are struck with the sword, when the enemy is stabbed with soul edge, the victim is faced with utter illusions of how they can/will die.
So in my case... If I am stabbed with soul edge, the blade will show me an illusion of me being imploded in the white void. Every blow is final, and if the target has no soul, then nightmare would just consume the target's essence in the gaping hole in his stomach. Nightmare can only be controlled by someone who has a geass. And the affects of the illusion are not "jutsu" so they are irreversable.