Third scum, because third party can be anything. Literally anything.
Here's another one for you to try on
If there was a no-killing third party with a wacky win condition in this setup, and I was given it, I wouldn't play it. I would have dropped out and told Laggy to find a replacement, because that would be broken as heck. There is no way town can tell it exists, or what remotely it can do, or how they should go about finding and stopping it. You can call crazy theories all you want, I dunno, maybe every townie is secretly a third party. What you're effectively doing there is criminalizing good town play.
I'm not interested in even entertaining any third party theories like that. If one exists in the game, I quit, I'm not it and I'm not looking for it.
I'm looking for a third scum.
Yeah it's pretty ridiculous but this setup is pretty ridiculous already, we either have a bogus third party or a scum that's been no kill gambiting with a ghostly third vote that they can use at will, and indeed the setup is 8/3 as you said. No matter how you slice it the setup is whacked and I am incredibly disappointed with Laggy. But that's for aftergame. For now Kilga's the best bet for third scum.