Set is not a dark god so much as he is a god who has been violent in the past. Set is a god of life more than he is a god of death, but few people will go beyond the superficial information about him all over the net and in most books. Most people are willing to call him dark and evil due to his murder of his brother and his bullying his nephew/brother.
Set's murder of Ausar has been linked to the difference between the two, in calling Ausar life and Set death. This is simplistic view and does not take any real depth to think about. Ausar, yes, is life, but he is also death. He is the life that comes to one after one is dead. Set, however, is the death that comes at the cost of life, or put another way, he is the life that causes death. In every moment, beings live and die all the time, it is not so strange to link the two in a dance together. And beyond that, Ausar needed to die, otherwise he would not rule over his section of the Duat, giving places for a person to live after death, and he would not go with our friends and family and keep them company in their death. Ausar is the only god who is dead, and because of this, he can be closer to the dead than any who are alive can. Ausar is a passive god, while Set is an active one. They compliment each other and complete each other.
Set is a god who, at times, represented the night, but even so, you might want to focus upon actual gods of the night, rather than gods who represented the dangerous things that lurk at night. There is a reason why Auset cries out about what Heru the Child's brother (Set) has done to him when he is stung by scropions and bitten by snakes.
Set is a god who was adopted by Hyksos (foreign Asiatic invaders) and due to their vernation of Set as similar and/or the same as their god of thunder, lightning, and storms, when the invaders were removed, Set was deemed as evil.
Before that, he was something of the other side to both of his brothers, and he even had a relationship with his brother Heru (if you need more information on what kind of relationship, feel free to mail me as I refuse to discuss mature topics where virgin ears lie). Heru is at times his brother and at other times his nephew. Part of this involves the title brother that was used between two people with mutual attraction towards one another.
Another part of the title of brother lies in that Set represents night, Heru represents day, Set represents chaos, Heru represents order. By chaos testing order by pushing against it and trying to overrun it, this shows the idea that chaos (true chaos) can attempt to move beyond the boundaries order (true order) gives it. Chaos' defeat by order, and subsequient control by order not only represents that chaos cannot overrun order, but also that chaos can be brought under heel by order. Order can learn to use chaos constructively, rather than seek to destroy it. Chaos can benefit by being placed under order's command, in that chaos no longer causes itself shame by its reckless nature.
I have also seen his bullying of Heru as worrying whether Heru is worth his salt or is merely a child grasping for something that he does not truly deserve and has yet to earn. To me, this would stand to protect Kemet (Egypt) or civilization from the harm caused by the immature and irrational running things (not at all to say that all children are immature and/or irrational). Set protects life from becoming even more painful and horrifying than it already is, by testing his nephew over and over again, and forcing Heru to prove himself as a man.
Set and Heru also compliment and complete each other, just as Set and Ausar do.
The myths are stories. Stories are intended to teach. Please do not take the myths as literal fact of how the gods are and assume they are this way or that way merely based on stories. Especially not stories as silly as The Contendings of Heru and Set . Within that story, only Neith, a bisexual (meaning a manly woman) goddess of war and agriculture flattered as Great Mother of All the Gods, managed to escape some form of ridicule.
I personally find Set more of the "Don't whine about it, get off your rear and do something about it because I sure as spit won't do it for you" kind than "Sure, I'll show you..." But that is just me. Working with someone like Djehuti (Thoth), or Auset (Isis), or Heka ( the God of Heka aka magic), or Werethekau (Great of Magic, sometimes a title, sometimes a goddess) may be better for any sort of magic involvement, simply because they will be more knowledgeable about anything regarding magic. Not to say that Set is not, he just seems like he would be less willing than the others to share what he knows and his power. He is more of forceful god than anything else, but his force is not without reason.
Nut would be a better Kemetic goddess of night in her aspects of Nut as the Night's Sky, Devourer of Her Children, Mother of Re, and Devourer of Re.