Alicornutopia

pffffahahahahahahahahahahaha

Damn, I already was quietly shipping them both.

Would Nivah and Aji still do this if they weren’t blue-group, or would they then consider it not worth wasting the two forms on?

They'd probably still do it, but it's more appealing with forms to burn on it.

What would happen if a vampire (Elcenian or otherwise) tried to drink from a Names!Fairy? As far as I can tell, it would be as follows, but some of the order of operations might be wrong:

1. The vampire bites the fairy. So far, this goes as usual.
2. If relevant based on the type of vampire, some venom gets into the fairy.
3. The vampire starts drinking.
4. As soon as any blood starts getting digested (whether that’s by saliva, magic, or whatever other process), the vampire is now the fairy’s vassal. If the vampire is of the Elcenian variety, they also have infinite lifespan at this point.
5. As the vampire is now the fairy’s vassal, they must stop drinking and remove their mouth from the fairy. They have had as little blood as it is possible to have from their attempted meal.
6. If there is any venom involved, it still takes effect. I’m not sure what Aurum!vampire venom would do to a Names!Fairy. Would it be like with a human, turning them into a vampire in addition to their fairy kind? What does Aurum!vampire venom do to nonhuman nonwolf animals?

Is the list right? Am I forgetting anything else that should be happening here?

Almost completely right. Elcenian vampires cannot acquire infinite lifespan by biting fairies. Aurum!vampire venom would hurt but not turn a Names!Fairy. Animals die from exposure to Aurum!vampire venom.

What happens if Talyn borrows some lifespan from a Names fairy?

Step 2 would vassal the fairy to the vampire, right? In which case step 4 would not vassal a (venomous) vampire to the fairy, since it's safe to accept food from one's own vassal.

Can you vassal a fairy by giving her some of your lifespan?

Venom does not count as food.

You cannot vassal a fairy by giving them some of your lifespan; the working probably wouldn't even function in the first place but if it did still no.