One of the prerequisites of godhood in Anglo-Nordic thougth is benevolence toward divine and human society, so there has never been a *deity* of evil. "Evil deity" is, like, an oxymoron. Loki is no deity.
Evil is a word Germanic in origin and references any force that works to breakdown the organic wholeness of an organism (eg. an individual) or macro-organism (eg. a community). First and foremost, it is an action with intent forming a mitigating factor, and as the Sayings of Odhinn state, "no man is so evil that he is not without some redeeming quality, nor any man so good that he is not without some fault", so it is not surprising that there is no comicbook-like being that is cast as evil incarnate in Germanic myth or legend. Afterall, many forces work to breakdown the (w)holiness of a society, from the mindless forces of nature (which lack intent) to other societies, and even a medical doctor must often cause small harms in order to effect an overall cure, eg. surgery.
In ancient Germanic crime and punishment, there were two forms of execution for capital offenses. The first, reserved for "criminals" and closely associated with Odhinn, was death by hanging. The second, reserved for offenders whose crimes were also shameful in nature, was death via submersion in a bog. Archeological evidence also indicates that such shameful offenders were ritually multilated prior to submersion and this is further shown by the Germanic treatment of the "spoils of war" prior to the Migration Age... which was all brutalized and thrown into a lake or bog as a wergild (fine) of sorts for the crimes of warfare in that day and age. These would grow into the cursed treaure hordes of Beowulf and the Volsung saga.
So, no, there really is no Nordic Satan... no boogeyman. Loki would come the closest, and Fenriswulf might come even closer still... as he exists merely to consume for his own selfish ends. Both could easily be called evil, but in the end, it mattered much less what a things "inherent character" was (how is that determined anyway???), and more how their actions effected society.
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Powersurge (history, pics) [
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Morningstar (campaign journal) [
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"You just decided *all by yourselves* that you are the Earth's protectors. And that you, and *only* you, not your teammates or family, are trustworthy enough to include in the process..."
T'Challa, The New Avengers: Illuminati 1