How do certain vampires look truly human? Some examples are Jakben, Earl of Imbel and Seridur.
We all know from playing as vampires that regular drinking of blood lessens your wrinkles but you still maintain visual evidence of being a vampire such as red eyes. So how do Jakben and Seridur haven no visual evidence of vampirism?

My guess would be regular feeding and lots of experience passing for human.

Ugh....people only seem to remember the Cyrodiilic clan...Here's the deal, the Cyrodiilic clan is the only one that'll resemble their race, if they fed recently. Everyone else looks like a monster, born from the curse Molag Bal [censored] into the world. As for the red eyes and no red eyes thing, Seridur was the only one to have it, and that was more, I felt, to create a mystery. Too bad it wasn't difficult in anyway. Earl of Imbel did, though looked as though he fed recently. http://www.uesp.net/wiki/File:OB-npc-Jakben,_Earl_of_Imbel.jpg.

And the reason they get weaker when they feed is because that was likely the terms of the pact they made with Clavicus Vile. They're able to blend into society, at a cost of being weaker. But this doesn't make them any more weaker, they become even more manipulative. Because of this, they are able to rally common folk and warriors to drive away other clans that'll trespass into Cyrodiil. All the other vampires remain at a constant state of power, and always look ugly. You could say the real form of the Cyrodiilic clan is when you starve yourself completely, but their real power is the ability to blend into society, as long as they regularly feed.

Game mechanics. Seridur and Jakben, in their first appearances, are not flagged as vampires in game. This is for two reasons: A. your not supposed to know their vampires, and B. Oblivion makes it so that any npc with vampirism has maximum ugliness.

Damn you. I was suppose to explain to him the epicness of the Cyrodilic clan. No! It's my job. You can go ahead and tell other people the other lore stuff and whatever.

:P

Nah, I care little about vamps, only the continuity.

That's why I said you should help the other lore section. Leave vampires to those who care enough and undertand it more. I am not into continuity, not dark enough for my tastes.

But there was nothing else to do.