A giant crytals space ship crashed into Azeroth a while back. It irradiated a nearby lake and mutated the wildlife. The alien survivors set to work understanding the damage they'd caused. At times this was a violent process, gathering blood samples to study them. As they learned more, they found a way to clean the lake. Moving outward, they worked to inoculate nearby wildlife from the remaining radiation. In further stages they sought to understand the damage and limit further harm.
Contrast this with the night elf method:
Quest Giver: Demons have corrupted the poor widdle bunnies! You have to kill them!
Me: Sure thing!
I go off to kill a dozen demons and return, looking for a reward.
Quest Giver: Demons have corrupted the poor widdle bunnies! You have to kill them!
Me: Huh, must be bugged.
I go off to kill a dozen demons and return, looking for a reward.
Quest Giver: Demons have corrupted the poor widdle bunnies! You have to kill them!
Me: Third time's the charm?
I go off to kill a dozen demons and return, looking for a reward.
Quest Giver: Demons have corrupted the poor widdle bunnies! You have to kill them!
Me: Could you clarify that pronoun there? I think we're having some problems with the "them" that you want me to kill.
Quest Giver: You have to kill all the bunnies!
Me: Sure thing!
I go off to kill a dozen bunnies and return, looking for a reward.
Quest Giver: Demons have corrupted the poor widdle bunnies! You have to kill all the demons. And also some more bunnies.
Me: Why didn't we just kill the demons in the first place, then decurse the bunnies?
Quest Giver: Because I'm not secretly an ambitious demon using you to kill bunnies and my rivals.
Contrast this with the night elf method:
Quest Giver: Demons have corrupted the poor widdle bunnies! You have to kill them!
Me: Sure thing!
I go off to kill a dozen demons and return, looking for a reward.
Quest Giver: Demons have corrupted the poor widdle bunnies! You have to kill them!
Me: Huh, must be bugged.
I go off to kill a dozen demons and return, looking for a reward.
Quest Giver: Demons have corrupted the poor widdle bunnies! You have to kill them!
Me: Third time's the charm?
I go off to kill a dozen demons and return, looking for a reward.
Quest Giver: Demons have corrupted the poor widdle bunnies! You have to kill them!
Me: Could you clarify that pronoun there? I think we're having some problems with the "them" that you want me to kill.
Quest Giver: You have to kill all the bunnies!
Me: Sure thing!
I go off to kill a dozen bunnies and return, looking for a reward.
Quest Giver: Demons have corrupted the poor widdle bunnies! You have to kill all the demons. And also some more bunnies.
Me: Why didn't we just kill the demons in the first place, then decurse the bunnies?
Quest Giver: Because I'm not secretly an ambitious demon using you to kill bunnies and my rivals.