Under the ruins of the old castle lies the Great Evil from the past ages, sleeping lightly, waiting for the moment to appear and rain destruction on the earth. For now, it has no possibilities for awakening - it seems to be too weak, but day by day it grows stronger and could eventually shrug this sleep off.
Brave heroes, ready to battle, come into the castle - here are many reasons for them to do this, from just looting the abandoned keeps in the ruins, to patrolling the woods to stop bandit raids, etc. But they must be very, very careful, since having any of them dead will fuel the power of the Great Evil and shorten the time until its awakening.
And here's a problem: why only the heroes' deaths are counted here? They may kill a lot of creatures - but that doesn't harm in any way, the Evil feeds only on the "good guys". What could make the difference?
Some ideas I'm thinking of:
- Many of the "bad guys" are soulless (or even mindless, like giant jellyfish or undead). Great Evil gains strength only from human souls, it has no use for such garbage. But what about the mentioned bandits? They are bad, but not so evil to call them soulless.
- Heroes carry some kind of internal strength, which is not possessed by the "bad guys" - that's the reason they can win many battles in a row, but that's also why they are of interest for Evil. But I don't want to handwave it like this and can't yet think of some more detail.
Disclaimer: This question is based on the game mechanics (the story, in fact, is planned to be like "extended novellization", based of the game plot but adding a lot of details). I'm deliberately not including game's name in the question, so it doesn't influence the answers.