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The problem here is that by giving him a clearly understandable (even if evil, misantropic) goal, you're making your Fenrisúlfr more human-like. Sure, we can say - by rough sketch - that it wants ...
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#4: Attribution notice removed
Source: https://writers.stackexchange.com/a/38375 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#3: Attribution notice added
Source: https://writers.stackexchange.com/a/38375 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
The problem here is that by giving him a clearly understandable (even if evil, misantropic) goal, you're making your Fenrisúlfr more human-like. Sure, we can say - by rough sketch - that it wants to eradicate life. But to be truly " **so far from human comprehension**" we need to cut off any human understandable explanation from his actions. [![Agent Smith from the movie "The Matrix"](https://i.stack.imgur.com/qGZ2p.jpg)](https://i.stack.imgur.com/qGZ2p.jpg) Your question reminded me of [Agent Smith](http://matrix.wikia.com/wiki/Agent_Smith)'s speech in the Matrix about humans being infestant and nocive as viruses: a memorable scene, and surely a villain-nesque one. Smith is a villain and can be surely defined as evil from a standard ethic-point of view. On the other hand, most Eldritch abominations in Lovercraft's lore are able to make humans go mad just by _existing_. C'htulu and his playmates can make you mad and transform your brain into pudding by lifting a finger, but it's ever unclear if they do that intentionally or it's just a side effect. Cosmic horror is given, in the end, by the terrible randomness of it all, that challenges and questions our innate sense of cause-effect. By contrast, check this question on Worldbuilding's stackexchange about a somewhat good-willed abomination which _tries_ to avoid human going mad: [link](https://worldbuilding.stackexchange.com/questions/72958/how-can-a-horror-from-beyond-reason-reliably-communicate-with-mortals) So, the point that I'm trying to make is that we may as well synthesize Fenrisúlfr's goal as "wanting to destroy life", but we should stop at that. Why does it wants that? How does he plan to achieve that? Ultimately, the less we know, the more uncomprehensible he will be. The reader (and the characters) should ask themselves: _yes, it appears it's trying to destroy life, but are we certain of it?_ Sometimes Fenrisúlfr's influence should produce inexplicable effects, or straight up conter-intuitive ones (like giving power to a good, untainted character, or partake in the defeat of a human villain, or destroying a dictator in the midst of a killing spree...). That's because the way Fenrisúlfr perceives reality should be so alien from our own that we cannot possibly comprehend it. So, it may as well try to manipulate humans, but it must be done in a so subtle and a twisted way that it's not straight-up recognizable. In western culture, we have the idea of the tempting devil - Satan popping up from smoke, promising to grant us wishes if we do bad - but that's the very thing we're trying to avoid. Satan, in most portrayals, is simple: we undestand him roughly and man, he does understand humans _a lot_. So we can deal with him, and sometimes trick him into failure. But Fenrisúlfr? Its mind is so complicated that we can't grasp but a small portion of it. And, while being generally more powerful and intelligent than humans, there's a good chance that he can't comprehend us in the same way we can't comprehend ants. Our minds are substantially different. That may be a good reason why sometimes, Fenrisúlfr's plans fail: it just cannot comprehend fully human behaviour (after all, we're _alien_ to _it_). So, **in short,** my suggestion is: remember that when writing Fenrisúlfr, if you apply human-like desires or intentions to it, they should be only gross approximations. Make it random. Make it fail, if need be. Make it unforeseeable.