Quetion about monsters that aren't counted in the kills %

Hey, I saw in plutonia&plutonia 2 map 11 that in the last sector there are archviles that aren't counted in the total monsters of the map, I think that there's such a thing in doom 1 E1M8 in the death sector with the imps, zombies&demons.
How can I add such monsters and how can I define that when the player has certain hp or when he dies the level ends, one of my ideas is to put in the end of my map a cyberdemon that isn't counted in the total monsters that you have to kill and once he kills you the level ends.

Monsters that aren't counted in the kill percent:
- Lost souls (except before v1.666)
- Commander Keens

Monsters that aren't counter in the kill total, but are counted anyway in the kill percent, allowing to go above 100%:
- Anything spawned by an "icon of sin" monster spawner
- Anything resurrected by an arch-vile
- Anything resurrected by the "Nightmare!" skill setting

Some source ports, notably ZDoom and derivatives, change parts of that (e.g., lost souls count as monsters and the kill total is updated in real time every time a monster is spawned or resurrected by anything).

GZDoom also contains a hack that excludes from the monster count those monsters that are spawned in a "death exit" sector (like used in E1M8). The rational, I think, was that usually we aren't really supposed to fight these monsters. This may be what you're thinking about. In that case, be aware that this is a feature only present in GZDoom.

Commander Keens DO count AFAIK

They do. It's boss brains that don't count as kills, despite being killable.

Indeed, I misremembered.