Cohan - who plays Maggie - told Entertainment Weekly that the third season's "body count is not done".
"That's pretty much all I can say, but we're not just going to see death," the actress explained. "There's going to be a whole host of challenges now that we've got the human threat.
"Woodbury is up to no good. The Governor (David Morrissey) is up to no good; it's really scary. We've got some scary stuff ahead."
Cohan also hinted at "crazy" scenes to come, as Rick (Andrew Lincoln) and his band of survivors run into The Governor and his Woodbury clan.
"In Woodbury, the Governor steps up and takes control because that's something he couldn't have gotten away with in the real world," she suggested. "And that has absolutely no limits."
Morrissey's villain made his debut in season three's third episode, while series regulars Lori Grimes (Sarah Wayne Callies) and T-Dog (IronE Singleton) were both killed off in recent episode 'Killer Within'.
The Walking Dead airs on FX in the UK and on AMC in the US.
> David Morrissey on Walking Dead: "There are big, big surprises"
> Walking Dead star Norman Reedus: 'Daryl is the breakout character'
Watch a promo for the new season of The Walking Dead below: