Being a lore nut that I am, I always wanted to offer up theories on possible meanings that also exist within the mysteries of the ES universe. For a time, we've seen mostly the Aedra and Daedra as this good/evil sort of view. While some Daedras are actually more benevolent than others, they are in no ways evil. There are exceptions such as Dagon though.
However, the look on Aedra and Daedra can be only summed up as Order vs Chaos. Chaos embodies change which is what the Daedra are known for, willing to do some unsavory actions that mortals do not like. Order embodies control and authority. Since Aedras embody both Anuic and Padomic qualities, I guess really they are the balance. Though not all seem to have these qualities.
Then there is Jyggalag, the Daedric Prince of Order. He is the opposite of EVERYTHING the other Daedric Princes think and believe. Calculative, logical and a master at deduction, always in control, and absolutely powerful. He sees the past, present and future. He wants to control that flow, that line, to have complete and total order. I dare say, he could not really be a true Daedric prince. He is a Daedra who does not embody change, and in fact, embodies complete and total control, holding authority on nearly the whole of Oblivion.
What is Jyggalag anyways? He certainly isn't Aedric because he has no chaotic quality to him. He certainly isn't Daedric at all, so what is he really? I could say he is the only deity to embody only Anuic qualities but I don't want to say nothing for sure.
While the Aedra certainly are seen in a positive light, they come from both Anu and Padomy. Daedras are often seen as a negative light because of how dangerous they are and how destructive their actions are. Jyggalag though, we know almost absolutely nothing about. We still don't know about him during Skyrim, and we were expecting some lore reference to that.
My guess is, he is still building up his own realm now that he has given it to the Champion of Cyrodil, who took up the mantle of Sheogorath. But that is a discussion for another time.