We have added a new rule for combat that allows a "death blow" when an opponent (or another member of your team) is near death. The unrefined rule as copied from the PH (edited for clarity):

NEAR DEATH - A CHARACTER OR MONSTER NEED ONLY HIT SUCCESSFULLY TO FINISH OFF AN OPPONENT.  This includes the unconscious, poisoned, sick, and lame.
Character will make a Mind (INT) Check, if successful they will see the opponent is near death and may strike the death blow.  Target may roll a resist (save vs death) check to see if they avoid instant death, but if the minimum damage done by a weapon is more than their total remaining Body Damage they will die anyway. This can be used to end the suffering of a PC on your team, an enemy combatant, or monstrous enemy.  This can be also used as an attack against a sleeping foe.

How do you feel about these rules, and should we keep it in our combat system?

"If the minimum damage dealt is more than their body points" - depending on your system that might be redundant (if people die at less than 0), or is this a significant change because normally they'd just be unconscious?
Basically looks like you're codifying when someone is looking weak enough to be finished off in one blow. TBH if I were doing this in D&D or whatever I'd probably say the opponent is looking like they're barely standing etc. anyway, without bothering with a check? In some cases (e.g. they're unconscious) I assume I'd think it'd be obvious without a check.

Quote from: Bloody Stupid Johnson;1126445"If the minimum damage dealt is more than their body points"

The system allows for unconsciousness at 0, and death from bleed out at -10.  The check is more related to battle when you would not normally see that an opponent was close to 0, or if a target was down to give a chance to see if they are down or faking (as one race of character does).

I don't think its necessary. If a creature is near death, that should be obvious to the characters. The players should get the sense of how damaged their foes are by the GM's verbal description. "Which orc is bleeding the most?" is a free action that shouldn't need dice. The only time I'd use any kind of perception check is when the foe is so alien that its not clear if damage is being done. For instance, I've had demons, elementals and ghosts and other non-biological creatures not show any wounds in battle. At zero HP, they are destroyed, but until then, they appear at full strength. If a PC has a reason why they could discern the being's "health", then I'd make it a roll.

As for death blow rules, I've always found them in conflict with the concept of Hit Points. If you attack a sleeping foe in my OD&D, you get Advantage to attack and double damage, but then, if they're not dead, they're awake. Yeah, I know that's problematic with the ninja who sneaks in and slits throats, but the concept of escalating HP is supposed to protect "major heroes" from that ninja. Instead, Conan awakens bleeding profusely and then chokes the ninja to death.