The Sun as an Evil God

I was recently listening to a podcast in which (to paraphrase) it was stated that CS Lewis had once said that he could not imagine there existing a human poet who could use the sun as an image of evil. 

Lewis was referring to the fact that sun gods are basically always benevolent and central in human mythology, for the obvious reason that human beings have always known themselves to be totally reliant on the sun. But this immediately got the cogs of my mind whirring in a 'challenge accepted' sort of way: what would a civilisation look like which understood the sun to be an evil god?

Well, what if that civilisation existed on the planet Mercury, where the sun's light and heat would be totally destructive of human life? This would, as it happens, chime very nicely with my recent thoughts about a fantasy version of Mercury as a D&D sword-and-planet setting, and its 'vanished moon'.

The central conceit: the sun is actually an evil god for the planet Mercury; the setting is also haunted by the existence of a vanished moon, which is understood by the different Mercurial cultures in various cadences as a mysterious symbol of goodness. 

General thoughts:

• This a sword-and-planet setting so there is no reason for it to incorporate any hard SF elements, but it is notable that Mercury in effect has a day lasting 88 earth days (and a night with the same corresponding length). The number 88 has a nice symmetry, obviously, but what I like about this is that implies the existence of nomadic surface-based civilisations which travel around in the cold night, permanently staying ahead of the sun and presumably herding all sorts of exotic alien migratory animals.
• It probably goes without saying that on the sunny side of Mercury there are continuously summoned into being various light-and-heat demons who sometimes stray into the dark side to run amok. Perhaps there are even entire evil nomadic civilisations which are the counterparts to those on the dark side.
• There would also likely be cultures which make their homes underground, so as to have some stability. Mercury also has permanent ice caps because there are large polar areas which are always shrouded in shadow due to cratering (one of these craters is even named after Tolkien), so one could envisage the existence of glacier-cities.
• The inhabitants would probably navigate by echolocation or perhaps just having the ability to see in the dark; maybe this indeed represents some fundamental division, with Mercurial dwarves and elves using innate magical sight, and humans navigating by sound. Althought a competing possibility would be that the human population navigates using sight and has to try to conjure or create light sources in order to survive. 
• Good is represented by the absent moon, but this reveals itself in many different ways in different cultural contexts - one culture might be ruled by a feudal network of 'moon knights' who purport to protect the people from the demons of light-and-heat, whereas another might have a traditional religion hinged around the veneration of (long disappeared) lycanthropes, and be characterised by its people taking on the aspect of a wolf, bear, etc. in imitation of lycanthropy. 
• It may also be the case that there are beings which are capable of surviving both Mercurial day and Mercurial night, or perhaps of living in the liminal space between the two, at Mercurial dawn and Mercurial dusk. Indeed, it is possible to imagine people being able to live in one of those crepuscular states, having enough light to live by, and continuously moving so as to stay one step ahead of the morning (or night).