Simulating empathy on demons with magic.

Imagine a demon when they attack someone will mirror the sensation their victim feels. This effect would be applied by a magic spell immidiately and without fail. Ensuring they understand and share all the pain caused. In turn prompting them to mentally calculate that toll on their next victim ahead of time and be dissuaded from carrying it out as it would hit them aswell. Effectively simulating pain empathy as they are literally sharing pain of others.

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Assuming we give all demons pain empathy with such a spell. Will they...

• Kill us anyway and hurt themselves more and more from the spell?
• Spend a long time gaining our trust to get released from it?
• Ally with some evil human group to deal the damage for them?
• Go into hiding and analyze the spell untill they could break it?
• Give up and start doing something else?

Would the answer change if we added a clause that killing a human causes not only pain but also death?

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*To be clear, I am not advocating for this. Even if this works, killing them is better, cuz they're evil.