For your first question, I am under the impression that you believe that "good" and "evil" are labels that everyone can agree on. My purpose is to persuade you that they are relative, and therefore useless. I cannot agree with you that Dagon is evil, because Dagon himself would disagree with that statement, thus proving that our "evil" is not universal. (Besides, he's a force of nature not unlike Alduin; see below.) The problem is that, when we speak of "evil" and "good," we speak in universal terms--morality is something we are taught to believe is universal, and the terms "good" and "evil" are taught to us as though there is an objective good and evil to be found. There isn't, simply because every person that history has labeled "evil" obviously would disagree--or else he would not be doing those "evil" deeds in the first place.

I am not an economist, but those "heavy-handed" trade politics you refer to are exactly what I'm talking about. And ignoring those, let's not forget that the rise of industrialization (which is connected to trade) led to a great deal of suffering for the working class, both in the past and the present. Trade is as "evil" (by our society's standards) to the victim as it is "good" to the person who benefits. Consider that, even in the modern world, trade practices (specifically the trade of money) have only just recently given us a five-year-or-longer recession. Trade is good for the people making money, and evil for the people losing money--and thus, the terms "good" and "evil" are again useless in this discussion.

You're right: TES is a fictional world, but that doesn't mean that we shouldn't hold it to the same standards in which we view real life. I have come to look down on stories and settings that have entirely "evil" characters whose only purpose for existing is to cause other people pain; that much is, admittedly, my opinion. One reason that I like TES so much is because I don't believe TES devs have resorted to that kind of plot device, or at least they haven't in a very long time (Jagar Tharn is probably the most stereotypically "evil" main villain the series has produced, and even then, he obviously values his personal "good" of gaining power over the "evils" he perpetrates to do it, assuming that he even views his actions as "evil" anyway--while the rest of Tamriel doesn't agree, being his victims and gaining no benefit from his actions, it doesn't make his opinion of the value of personal power any less valid). Therefore, I am happy to judge TES based on real-life standards, at least when it comes to player morality (especially when we have learned from TES history that people who, under our society's standards, are guilty of "unspeakably evil" acts have capitalized on their actions in order to achieve some form of godhood or another).

As for Alduin? When he eats the world, as in background lore, he does his cosmic job; he is no more "evil" than a hurricane or tornado in that respect. When he dominates people, even if he is not doing his job, he nonetheless has his own reasons for it, reasons that he considers "good." Do we necessarily care about the wants or needs of the fish that we pull from the sea, when we're hungry? Should Alduin care about his meals? If he should have more satisfaction dominating his food rather than eating it, so be it; as far as he is concerned, the benefits he gets from it are more "good" than any "evil" he might do to the food in question, and that assumes (most likely falsely) that he considers anything he does to humans as "evil" in the first place.

Well as Dagon's representative Mankar did fulfill his promise to the Cultist about the Paradise. Of course he wasn't joking about the whole being "tested" thing and many of the Cultist didn't expect how hard it would be.

Uhm. This is embarrassing, but I actually was editing my post all this time and just refreshed the page.

1. I answered a bit of this, in that I stated what I thought you meant and what I meant in return, but I'll repeat my purpose because it has a bearing on the rest of these questions. I'm trying to explain how "good" and "evil" are useless terms by proving that they are opinions and therefore relative, when their definitions (or at least their common use) indicate that they should be universal. The Daedric Princes are probably not the best examples I could use to prove this, since I can use a completely different rationale for them (as they are basically forces of nature, they are no more evil than a tornado, as mentioned above); that said, when considering them as individuals or persons, one could imagine a child with an ant farm, and think of the ants as mortals and the child as a Daedroth. Our society would not condemn a child as "evil" for snickering, or even poking and prodding, at creatures that are so far below that child as to be inconsequential. To the Daedra, we are nothing, and they have no reason to believe that our interests should ever equate with their own. The fact that the Daedra themselves do not hold to our morality proves that our morality is not universal--though that's obviously just in TES, as that is where the Daedra exist. As I said, they are usually better explained through much different rationale than when I compare mortals to one another.

2a. If one believes that society is "good," then those things that have an ill effect on society are therefore "bad." However, I attach no more moral value to society than I do anything else; it exists, and it has personally served me pretty well (I know better than to think that I would have survived without it), but that doesn't make it "good" (because, after all, society's protective blanket over people means less food for the lions, so obviously it's not "good" for them). Those things that detract from society are not therefore "evil."

2b. I don't deny that certain Daedra have an element of "MacBeth-ism" to them, as you describe. But let's remember, MacBeth benefited from the murder he committed (I haven't actually read the play, so I'm going off of the synopsis I remember from a few years ago and your own description here). MacBeth would therefore view his actions as "good," because he values his own power over the harm he has caused others; obviously those others would disagree. "Good" and "evil" are not universal values, as stated before; I repeat this, because my purpose is to put them to the side and discount them, and realize that when one says, "This man is evil," what he or she means is, "I personally do not like this man's actions"--yet what this person believes is, "Everyone else should agree with me," and that is only rarely true (and, in the case of actual people rather than fictional characters, is never true at all, because the person in question obviously does not agree with the judge's assessment).

3a. As I said above, I like TES for many reasons, and one of them is because I enjoy its usual unwillingness to fall into "good" versus "evil" trope-fests. But the king you use as an example sounds like a real-enough person to me to judge him as I would judge a real-life king who has done the same things. Now, the king who taxes his people for the sake building more castles would not do so for no reason. Perhaps he just wants something to do, and values his enjoyment more than he values his people's safety and security; most people who are not the king would believe that this is "evil," and I would say that it is unwise and hardly conducive to protecting society, but for the king himself, his comfort is important enough to sweep away any other objections--it is "good" for him to build castles for the hell of it. Castles are also defensive structures; having more of them would be considered "good" by a military strategist on his side (if we can assign moral labels to military adventures, anyway). The king who chooses to close all of his hospitals and leave his people to fate is doing a "good" thing in his own mind because (among other reasons, which may be religious or lay in nature) hospitals cost money, so he's saving plenty by closing them; or more speculatively, the afterlife might be a good place in his religion, so more people dying means more people in paradise (which is good for them); or for any number of other reasons. The point is that the king will always have a reason for doing what he does, regardless of whether or not anyone else agrees with it, and therefore he will believe that his opinion is "good" unless persuaded otherwise by an outside opinion who he values more than his own (for reasons that are, again, "good" in his opinion).

As for the "margin of rationality" you mention, I don't think it matters. Rationality exists for every action; more to the point, you might easily disagree with my rationale, and vice versa. As an example, imagine that I said, "I want to gain power, and you're in the way, so I'll get rid of you so I can do what I want." My rationale for this is that power is good, and not everyone can have it, so some people have to make way while others (in this case, hopefully myself) can have their cake and grief counseling. You would (most likely) disagree with me that my desire for power is more important than your desire to live; however, that does not negate the fact that my example-self has put forward a rational, if self-centered, argument. For others to call it "less reasonable" than other rationales is, sadly, a matter of opinion; you cannot prove that my desire for power is not as important as I make it out to be.

3b. I have explained Alduin in the previous post. Miraak and Harkon are more interesting because these two cannot be handwaved as forces of nature, but are instead individuals with their own ambitions and reasons to do what they do. Most of this comes down to power, as mentioned before. Quite simply, they believe that their desire for power is more important than other people's desire to live. (Note that I have never played either Dawnguard or Dragonborn, but I understand the basics of the plot... I think. In Miraak's case, he also has the desire to escape his prison; and Harkon no doubt wants to avoid being vulnerable just by stepping outside on a sunny day, which in my opinion has some justification to it.) Who is to say that they are right or wrong? The fact is that you can only persuade them by killing them--which is to say, you resort to force rather than arguing the case with them. There is nothing that makes your case more "right" than theirs, except that you killed them before they could kill you. The Dragonborn does not prove his "rightness," his "goodness"--and he does not prove his enemies "wrongness" or "evilness"--by killing them.

You skipped 4. The only reason I point that out is to explain why I'm moving on to 5.

5a. Molag Bal obviously believes that gaining Logrolf's service is more important than Logrolf's desire to remain free (I've never played the quest, and am going by your description--there is a pattern in this, I believe). Mortals might view this as "evil," especially since it could so easily be them in Logrolf's place. Molag Bal obviously thinks differently. Again, morality is not universal--even in this fictional universe.

5b. Morality has nothing to do with practicality or need. I could say, based on my memories from UESP, that there is a whole society of cannibals in Skyrim, and having feasts like this is a way of maintaining friendships--a "good" that our own society supports, as well. But the only "good" here that really needs to be fulfilled is the cannibals' and the Daedric Prince's. The Prince thinks her enjoyment is more important than mortals' lives, and so far nothing has proved her wrong. The cannibals apparently enjoy being cannibals, and therefore believe equally that their enjoyment is more important than anyone else's lives. You and I can disagree with their decision, but that is our opinion, not a stated fact. (And I should point out that with this example, as well as the other examples of "common evils," that my opinions and yours probably aren't vastly different: I don't like murderers any more than you do. I just acknowledge that my dislike of murderers is my opinion, not a universal truth.)

5c. Like the above example, Vaermina apparently gets something out of it, and this is more important to her than worrying about the suffering of mortals below. Or I could handwave it by saying that she's a force of nature like the other Daedric Princes, and even the Aedra, and blaming them for doing their own thing is like blaming the hurricane for existing. I don't like the handwave, but it does fit in this instance.

I dealt with trading in my previous post. As I said, I'm not an economist, so I'm sure you know more about it than me if you're studying economics. And I'm sure that there are plenty of theories that make trade work absolutely great. In practice, however, those theories either haven't been implemented or have otherwise been twisted for the benefit of some over others. Either way, our world right now is pretty skewed in no small part due to trade, and once upon a time it was much, much worse.

Edit: I can't believe I just spent an hour and fifteen minutes working on this. Time flies.

The way I see it, good and evil depends on perspective. Doesn't mean I'm not allowed to call anybody evil.