So I was thinking: through the sun and stars, magicka streams from Aetherius to the Mundus. How is it connected to the light?

I've never heard of magic being less effective at night or inside caves. So the light can't be magic. But what happens in every game when we cast a spell? Colorful visual effects. Could light be the wasted energy of a spell, like heat is the wasted energy of about everything?

Maybe all light is created that way. The conversion from aetherius-magic to mundus-magic creates the sunlight, different kinds of spells create slightly different colors (that's why similar spells have similar visual effects) etc.

http://elderscrolls.wikia.com/wiki/Magic_from_the_Sky may help a bit.

EDIT: In response to your other questions, I'm not knowledgeable enough to provide a sufficient answer.

The way I see it... If we look hard at the creation stories, we are going to see that those who built Nirn had nothing else but magic to make it from. "Physical reality" of Tamriel is pure magic - but limited (thanks to Lorkhan's nature). This is why alchemy works. So, everything is magic, including light. Light - sunlight for sure, at least - is the least bound/limited form of "material" magic because Magnus has escaped the material prison.



Gameplay!=lore, but one of the most awesome aspects of TESII:Daggerfall chargen was the ability to choose how your character's magic abilities depend on the environment. You could get "light-powered magic" or "darkness-powered" - which translated to more spellpoints in preferred environment or to only being able to cast spells in the preferred environment. Spell absorption was also a choice that could be checked against the environment - you could choose spell absorption "in light", "in darkness" or "general".


Artificial lighting, in general, did not really seem to count for "in light". //the actual implementation of this feature is a bit glitchy anyway...//

Granted, Daggerfall was released before the major rules of Aurbis were established, so technically "darkness-powered magic" would make little sense, but with enough misinterpretation, you could write a passable lore-friendly "scientific" explanation of your character′s backstory, even if it includes diminished spellpoints "in light" yet spell absorption being active "in light" only as well. Yeah that's my character =)
But in light of such customising being unavailable in later games, I don't know if it would make sense for any character but a specifically genetically engineered Altmeri experiment...

Darkness-powered magic could also be another name for Shadow magic.

Could be, but if we're anyhow trying to reconcile gameplay with lore, we have to consider if these types of magic are capable of casting spells with exact same effects or not ('cause in DF you can cast exact same spells regardless of your "light alignment" as long as you have the spellpoints)...
Do you happen to know which Shadowkey spells were shadow, and which ones were "mainstream"? http://www.uesp.net/wiki/Shadowkey:Spells

according to the lore article none of those are actual shadow magic spells seeing as they don't fit the description.

http://www.uesp.net/wiki/Lore:Shadow_Magic

Thanks! So unless we deliberately maneuvre around one part of DF gameplay, there is not that much we could use to support the notion of "darkness-powered" magic being shadow...

This shadow magic sounds deliciously quantum mechanics, though. Makes one wonder how it is related to Dawn Magic ™...