Honestly there's a lot of things about these creatures that don't make sense. Like, why do they all have horrible diseases? And how have they not gone extinct? (Imagine if all humans were born with the black plague or something). Yes, I know it's based on the original mythology (which you can read here if you're curious https://en.wikipedia.org/wiki/Tanin%27iver but made more sense there.
If you want a justification as to how they haven't gone extinct yet the easy one is that their curse or whatever happened in recent history. Recent by dragon standards anyway, it could easily be a few centuries. Populations don't vanish instantly when their reproduction falls below replacement rates, it takes generations.
For remove curse/disease or heal to not work it needs to be a GM-fiat level curse. Like someone called for a god, any god, to save their family and it was Urgathoa that answered.
For remove curse/disease or heal to not work it needs to be a GM-fiat level curse. Like someone called for a god, any god, to save their family and it was Urgathoa that answered.
That was my headcanon as well. Some god or whatever associated with disease (presumably either Apollyon or Urgathoa, not sure if there any other disease related gods or the like) put a curse on them and that's why they all have diseases.
They're examples of what happens when a dragon isn't immune to its own breath weapon.
The dudes are walking bioweapon factories.
You can't cure their diseases because they aren't catching it from elsewhere; they're literally producing it from their own bodies. So even if you manage to be boss enough to pass the DC 27 caster level check to land a cure disease spell on the dragon, it's going to be immediately re-exposed to all of the contagions it passively produces.
They also have negative energy affinity, so a heal spell would just hurt them without fixing anything.
To "cure" themselves they'd need some power that granted constant disease immunity or suppression, like the antipaladin's plaguebringer power.
Which means a periapt of health would hypothetically do it, though I'd say a taniver wearing one loses access to both its breath weapon and the disease rider on its natural attacks.
The dudes are walking bioweapon factories.
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Interesting description. Makes me wonder if they were created for that exact purpose, whether by a disease god, an evil spellcaster (The Runelord of necromancy maybe?) or something else.