Preston, who plays Arlene, explained that there are lots of new creatures in future episodes.
"Of course the werewolves are there," she told E! Online. "Witches are going to start coming in at some point. We've got the fairies coming. There's never a dull moment on this show!"
However, Preston explained that Arlene will not become too involved in the supernatural just yet, saying: "Right now, she's fully human. She's a little scared about the whole supernatural world but she is grappling with a very human thing this season."
Preston added that she was impressed when she watched the season premiere.
"They just showed us the first episode of the season that they edited all together, and we were all blown away," she said. "I'm on the show about the bar, somebody else is on the show about the vampires [and] somebody else is on the show about the werewolves.
"It feels like we're on all these different shows, so you don't really know how it's all going to come together until you see it. We did - it's pretty thrilling."
True Blood returns for its third season on June 13 on HBO.