Basically, when it was Antonia's turn at the stake, she used that spell -- from the first time Marnie time-travelled or remote-viewed or whatever -- to pull every vampire within twenty miles around out of their sleep and into the sunlight. Priests, nuns, Olivier's Maker, all of them. Just walked out, their bodies were not their own, they met the sun, and that's why Bill sent Eric to MoonGoddess, and that's the thing that Eric and Nan ignored.
Bill: "Vampires have often found it advantageous to maintain a hidden presence in humanity's most powerful institutions. And in the 1600's that was the Catholic Church. And today, as you all know, it's Google and Fox News."
Which is a funny line, but short-sighted and bizarre in context, since we've already seen plenty of FoS bullshit on Fox News. You can't have your metaphor both ways. I mean, one of the things that's great about this show is that it regularly does, but in this case it's actually contradicting itself, not being ambiguous. Whatever. Cute line.
Anyway, Olivier tracked down all the witnesses, glamoured and killed them, and now 400 years later all the Sheriffs are getting it and they're ready to take out the witches. (Pam's ear drops off at this time, making the ticking of the clock on this one all the louder.) But they can't kill Marnie, as Pam explains, because she gave Eric amnesia and rotted her face and...
Bill: "She fucking what now?"
Pam: "Oh, shit. Yeah, the jig is up. Eric's got witchnesia and he's staying at Sookie's and I've been lying to you on his behalf which is no surprise, but it also means that Sookie has been lying to you on behalf of Eric Northman, which..."
Bill: "...Burns and goads mah heart like the rays of the sun, yes. She lied to me and then she lied to me about lying, which is so much worse. Mah heart is breaking. Ah must go."
Bill goes zooming off to do who knows what, and it's so dumb but even in this fun frothy campy episode there's a moment where Pam stares off to the side and the camera zooms in and she whispers to herself, "I'm sorry, Eric..." as though we're about to cut to a commercial for one of Marnie's stories, and we're done.