My guess is concentrated sulfuric acid (H2SO4)

It's Seithr Oil

Seithr oil is a fictitious substance.

Rainwings are a fictional creature

Fair enough. But WOF and Inheritance are 2 different universes.

Also a fair point.

CROSSOVER!!!!!

(Actually, I wonder what that would be like)

It's the kind that melts stuff

If RainWings existed irl they'll either have special fangs or be immune to their own venom or they'll kill themselves

hydrochloric acid. their mouth is lined with a membrane of mucus so it doesn't burn them

or gastric acid

I say it’s Sulfiric Acid because of the speed it burns skin.

“Damage induced by concentrated sulphuric acid appears within the first minute. Full skin lesions are observed after approximately 4 hours.“
https://www.cdc.gov/niosh/docs/81-123/pdfs/0577.pdf

hmm...

ok you're right

but hydrochloric acid can also inflict 4th degree burnshttps://www.healthline.com/health/hydrochloric-acid-on-skin#burn-side-effects

i just realized the absurdity of discussing fictional science with someone on meme website

concentrated hydrochloric acid i mean

not sure about the speed though