Karma lore/quest for not killing animals PvE
You realize you purchased a game called Guild WARS? I mean is this a serious question?
If you dont want to kill anything your playing the wrong game.
You could be on to something as far as some minor extra, such as an achievement for going a month without killing an animal, perhaps. However, discouraging players from taking certain actions or killing certain types of mobs is not a recipe for fun, and would just be annoying game design for most people — especially when you have daily achievements for kill variety, not to mention aggressive wolves and such who attack you on sight. What are you supposed to do, just run away from them every time they aggro you? Detour around packs of animals, possibly getting cut off from where you need to go? Besides, I can’t count the number of times I’ve accidentally hit some bystanding animal who happened to be wandering next to a fight I was involved in. As a ranger, my main axe attack automatically ricochets to multiple targets — not to mention traps and other AoE attacks. I don’t know if this would be possible to achieve, even if I wanted to. Heck, how would I ever have TAMED half my pets, when they’re typically buried in a cloud of unfriendly peers?
World of Warcraft had a small group of animal-loving NPCs who would dislike you if you attacked any animals in the vicinity. It’s a cute idea in the context of that one zone, but it really didn’t add anything to the experience, nor did it make the game more fun or meaningful. It made it a hassle. What you’re proposing might be a good idea for a different kind of game, but as is it would be a major obstacle for getting anything done.