Michael Ausiello with EW elaborates on Erica Durance as “Isis”, and more on Allison Mack’s return this season:

Question: You tell us that Erica Durance is playing Isis on Smallville and you don’t elaborate? WTH? —Steve
Ausiello: Do you still not understand how this works? Ausiello TV is where the seed gets planted, and Ask Ausiello is where we watch the flower grow. Put another way, Ausiello TV is the foreplay to Ask Ausiello’s full-on shag. So whaddaya say we get down to business? “It’s an inhabitation story,” explains exec producer Brian Peterson of the Lois-Isis connection. “Lois is actually going to be possessed by the spirit of Isis.” Was it good for you, Steve? BTW, quick clarification: Smallville‘s Isis isn’t the DC Comics character Isis. It’s the Egyptian goddess Isis with a nod to the DC Isis. Understand? Good, now explain it to me.

Question: Anything on Chloe’s return yet on Smallville? —Maria26
Ausiello: Allison Mack will appear in the premiere and then return “in the middle of the season in a very impactful way in Clark’s life,” reveals Peterson. “It’s a great wrap-up to her character, and it also dovetails into the Chloe/Oliver relationship.”

SOURCE: EW