'Asylum of the Daleks' sees The Doctor and the Ponds (Karen Gillan, Arthur Darvill) facing every Dalek incarnation that has ever appeared in Doctor Who.
Discussing the episode with TV Guide, Smith promised that the Daleks are more menacing than ever in their return.
"We have made the Daleks scary again, something I am not sure we got right before," Smith admitted.
Doctor Who showrunner Steven Moffat also opened up about the Ponds' exit from the series in episode five when they face the Weeping Angels for the final time.
Moffat promised that Amy and Rory's farewell will be a monumental moment for the sci-fi series.
"This, more than any other, is the year of the Ponds," Moffat declared, adding: "But yes, it's true, I cannot lie, somewhere out there, the Weeping Angels are waiting for them!"
Doctor Who kicks off its seventh series on September 1 on BBC One in the UK and BBC America in the US.
'Asylum of the Daleks' will be preceded by the mini-adventure 'Pond Life', which will debut its first of five parts on Doctor Who's website and YouTube channel on August 27.
Watch the cast and crew speaking about the upcoming Doctor Who 50th anniversary to Digital Spy below: