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In general, the answer is in your question — you said the "simple solution ... won't work". The trope is Simple Solution Won't Work.
First one has an element of You Kill It, You Bought It. It's simply natural to want to avoid that if you won't like what's being "bought". Could be a Discussed Trope if it's like:
- Alice: If you kill Charlie with magic, you will be forced to take on his curse of walking the earth picking fights for eternity.Bob: Oh, one of those 'You kill it, you bought it' curses. Absolutely no killing him with magic then.
Second one sounds like the spirits could have Resurrective Immortality.
No, I'm looking for the actual protection aspect.
Like the magical equivalent of poisonous/spiky/slimy/bad-tasting/etc. animals where killing them comes at great cost or is fatal, so they're left alone.
A better example of what you're asking for would be the Mark of Cain from the Book of Genesis. While retellings of the story treat it like it was a Mark of Shame, in its original context it was a warning from God that anyone who killed Cain would have vengeance visited upon them sevenfold.
The trope, if we had it, would be a subtrope of Simple Solution Won't Work, and a sister trope to Hydra Problem and You Cannot Kill An Idea.
Your Basket of Guts example really doesn't seem to me like the same trope at all. It just seems like Resurrective Immortality + Came Back Strong + Revenge. I feel like there's a distinct difference between "That guy has magic juju on him that will mess you up if you kill him" vs "If you piss that guy off and don't put him in the ground permanently, he'll mess you up himself. And he can come back from the dead, so nobody knows how to put him in the ground permanently."
Edited by MetaFour
In both cases it's "kill this person -> magic ensures you will inevitably die", it's just that the first has an extra condition.
A character is protected from direct harm on their life by something supernatural.
- In Wulfrik, the simple solution of killing the World's Best Warrior with magic won't work because his curse (to Walk the Earth looking for challenging fights, be tortured for eternity by demons if he loses) will then transfer to the killer, who prefer to be tortured to death than risk that.
- In Baskets Of Guts, the lich doesn't kill Anna because he knows that nature spirits Come Back Strong when killed, and get stronger with every defeat (as in needing armies to put down) until their killer is finally dead.
Edited by Chabal2