So, vampires here are created from humans with the help of a stone mask. Now, they're supposed to be weak for two things:

  1. Having their brains destroyed
  2. Prolonged exposure to sunlight

The first is obvious, for the second I came up with the following excuse, presented by Kyubey Mephisto:

"W-what happens if I walk outside during daytime?" She was clearly starting to lose it.

"It would be extremely painful for you. However, you wouldn't die right away. A vampire can spend hours in sunlight, but the longer you stay there, the more severe the repercussions become. The harmful effects of UV-exposure can stay for days and accumulate over time," said Mephisto.

"Why? W-"

"Shall I tell you?" Though Mephisto knew the girl was concerned about something else, he deiced to ignore it. Vampirification wasn't something he could or would do anything about. "What you're about to hear will fundamentally change your views of evolution and the place of mankind in it.

"As a vampire, you have become biologically immortal, meaning you can't die to old age. The same is true for your cells.

"You see, ordinary cells have so-called telomere regions in their chromosomes that degrade each time the DNA is copied. Once a limit is reached, the cell becomes incapable of mitosis and dies.

"This is not the case for vampire cells, which have ways of replenishing their telomere regions. However, this also means genetically damaged cells will be able to reproduce as well. Your body has facilities for repairing its own DNA, but sufficient damage could still overwhelm this ability, resulting in a slow death.

"When you expose yourself to UV light, it creates free radicals in your cells, putting oxidative stress on them, which means, you guessed it, damaged DNA."

So, this was my idea of explaining the weakness of vampires to sunlight, but it still sounds, weak. I mean, it is correct, but it doesn't sound severe enough.

What could make oxidative damage from sunlight even more severe to vampires?

  • $\begingroup$ getting skin cancer ? or something like albino african suffer under sun light thing due to lack of melanin? $\endgroup$
    – Li Jun
    Commented Mar 24, 2020 at 11:30
  • $\begingroup$ @LiJun Yeah, that's what oxidative damage is supposed to cause, but I want it to be worse than skin cancer. $\endgroup$ Commented Mar 24, 2020 at 11:31
  • $\begingroup$ found this when googling maybe you are interested xeroderma pigmentosum $\endgroup$
    – Li Jun
    Commented Mar 24, 2020 at 11:44
  • $\begingroup$ Self replicating telomeres doesn't lead to immortality by the way. Just saying. It'll take some of the edge off aging, but not all of it. $\endgroup$
    – Halfthawed
    Commented Mar 24, 2020 at 15:01
  • 1
    $\begingroup$ We should look to sociology for these answers. Vampires are vulnerable to sunlight because it has become a cultural norm for them. One can't even be a real vampire if he strolls about on the beach with short sleeves... he's just a cannibal weirdo. The overwhelming power of this norm seems like a biological limitation to those who are beholden to it, and they would argue incessantly that it must be so. None are willing to undergo the experiment to falsify it... why bother, when they know the truth? $\endgroup$
    – John O
    Commented Mar 24, 2020 at 16:14

3 Answers 3


Some types of porphyria cause extreme photosensitivity in the affected subjects, like X-linked dominant protoporphyria (XLDPP), Porphyria cutanea tarda and Variegate porphyria.

Porphyria has been suggested as an explanation for the origin of vampire and werewolf legends, based upon certain perceived similarities between the condition and the folklore. In January 1964, L. Illis's 1963 paper, "On Porphyria and the Aetiology of Werewolves," was published in Proceedings of the Royal Society of Medicine. Later, Nancy Garden argued for a connection between porphyria and the vampire belief in her 1973 book, Vampires. In 1985, biochemist David Dolphin's paper for the American Association for the Advancement of Science, "Porphyria, Vampires, and Werewolves: The Aetiology of European Metamorphosis Legends," gained widespread media coverage, popularizing the idea.[citation needed] The theory has been rejected by a few folklorists and researchers as not accurately describing the characteristics of the original werewolf and vampire legends or the disease, and as potentially stigmatizing people with porphyria.

Just take those and boost them, and you have your increased damage.


Vitamin D toxicity.

Humans produce Vitamin D in their bodies thanks to exposure to sunlight. Vampires do it as well, but at ridiculously higher levels, and since vampires are created, not evolved, that trait can't get selected out through natural evolution. Like humans, they need a little of it, but also, like humans, too much can result in things such as hypercalcemia (excess calcium in the blood) causing headaches, confusion, lethargy and fatigue, vomiting, nausea, excessive thirst, stomach pain, kidney stones, bone loss, and kidney failure. In some cases, it can interfere with heart function.

And for whatever reason, vampires are even more sensitive to Vitamin D overdose than your average human, such that blood calcium levels which might be concerning in humans but not immediately dangerous are much more severe in vampires, such as causing debilitating headaches. So their bodies are at the same time not very tolerant of excess Vitamin D and crank it out at absurdly high levels when their skin is exposed to sunlight (and we'll say that for technobabble reasons, it starts producing these effects much faster in vampires).

So there's your weakness: after a few minutes exposure to direct sunlight, they start getting debilitating headaches, feel confused, and start feeling nauseous, which obviously has negative effects if they're trying to do anything, and the longer they stay in sunlight the greater risk of kidney and heart failure.


How about setting your vampires' overall system like this:

  • low energy usage, so no good mechanism for heat shedding.
  • superblack skin absorbs nearly all photons, as this is advantageous when living solely in nighttime in cool climates.

Long daytime exposure: overheat and die.

This is not far from what happens to some lizards(I think) on the Galapagos, where large birds sit on them so they (the lizard) can't move. They overheat and collapse, easy pickings for bird-dinner.


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