I believe it is from "Immortal Blood" novel or several vampirism-related books on Volkihar or other species.

If it is not, then it's simple retcon.

Retcon.

Ugh...You again. Mr "They cut everything!"

double post

Not really, There has never been any info that says they can't walk in the sun because if there was, then it would be a retcon.
And in a way they do get harmed by the sun, just less so than other vampire bloodlines. I like both versions, weakness to the sun is good old dracula style, while the sun burning is kind of the modern take on vampires.

This is my opinion as well I appreciate both weakness to the sun even as a vampire in skyrim I don't go out in the sun when I want to explore or do quests the only time I go out in the sun is to sell my loot even if you don't burn to a crisp in the sun the -100% regen on magicka, hp and stamina is annoying.

A necessary inconvenience, Vampires do need their weaknesses because it is as much a curse as it is a gift. The only problem I still have with vampires is the lack of vampire strength and speed. I would also like to have the bat-like faces that npc vampires have.

This is what could have been done or could still be done.
Pros.
Vampiric Strength = X unarmed damage, X one/two-handed damage with X amount of chance to stagger or knockdown opponent. (gets higher the more you feed, stage four the limit though)

Vampiric Agility = Sprinting is faster, stamina drains slower at night, Jump height and length is increased.

Vampiric frost breath.

Mist form for human form.

Cons. In addition to current weaknesses.
Weakness while in a temple.(same as sun effect)
Unable to use silver or blessed weapons.(turn undead enchantments)
Unable to get blessings from shrines.
Only get well rested benefits through use of the coffin.
Need to feed to keep up benefits. (proper vampire feeding, not this reverse [censored])

I expected a proper feeding mechanic. Although, I am glad the stage four attacks are gone; it's non-sensical as you can't be a powerful vampire whilst also having the ability to recieve quests from most people in the game.

Although, there should be some attacks. At stage four, there's always a (reasonably high) chance of some Vigilants of Dawnguard attacking you outside of city gates. As well as this, regular ol' vampire hunters should be able to attack you inside city walls. I doesn't have to be limited to stage four, but the severity and frequency of the attacks should scale to the stage of vampirism you are in.

Here's my post on the feeding mechanic from another thread:

"Personally, I think that every day you don't feed you should become weaker. For example: if a vampire feeds regularly, then he/she takes minimal damage (I don't like the sun burning vamps - classic vampires just get weakened by it) from the sun and has very strong abilities. Everyday said vampire doesn't feed, he/she regresses a stage and becomes weaker - with more cons and less pros.

After four days of not feeding, the damage taken from the sun is at its maximum and your abilities at their weakest. Everyday after the fourth day, you loose 25 points in health, magicka, and stamina. This continues until you only have 50 points in them all left, meaning you'd basically be forced to feed because you're incredibly weak. Refraining from feeding altogether should not kill you for gameplay reasons, just severely nerf you. You should only have the ability to turn into a vampire lord in the third and fourth (possibly just the fourth) stage of vampirism. This would give us another reason to feed on regular intervals.

By sun "damage" I don't actually mean damage to your health. I mean your health, stamina and magicka are reduced (the severity of this varying on how fed you are) and lose the ability to regenerate them - just like Dawnguard, basically. Vampires should also have their sprint speed as well as their jump height increased. However, if one does not feed, it actually eventually means you're slower than a person without vampirism.

This, implemented correctly, would actually give us an incentive to feed rather than starve ourselves. Why would a vampire bother drinking blood if they're more powerful without it? Sure, there may be larger cons, but at the moment these are largely outweighed by the pros."

Stage four attacks being gone was good because like morrowind, it was a quest breaker but....random attacks from random vampire hunters, vigils of stendarr and dawnguards will be good. The more you feed the stronger you get and you will become more of a threat, so they attack you more frequently.

Post limit.