Do Something About Equestria, Dearest? Picture

And then they had sex. The end.

I'm now officially a fan of this pairing. If you really think about it, Discord/Eris could work as a myth, since in Greek mythology (that's where Eris originiated from, mind you) the Gods practiced bestiality and other unmentionables, so it wouldn't be random or absurd if a dark and evil Goddess like Eris decided to take Discord as a playmate, and due to how hot Eris is, I really doubt Discord would mind. Also, in my head canon, Discord prefers to have sex with human females, since he feels he could "Do more" with them. And they're actual villains, so you can't really expect their sexual interests to be normal.
Eris and the Apple of Discord
Nyx
Do Something About Equestria, Dearest?
Chaos Never Died
Nyx - Nox