What do you do when you're a part of a very successful franchise but have a chance to bring your pet project to cable television? If you're actress Amanda Tapping, who recently talked to our Jim Halterman about tonight's premiere of "Sanctuary," you make what she calls "this enormous leap of faith."

Tapping elaborated on how she came to the decision. "I had finished Season 4 of '[Stargate] Atlantis' and I got offered Season 5 and it was a really lovely contract. And it would've been very easy to say yes [since] 'Sanctuary' was waiting in the wings. We didn't have a broadcast deal yet. We were hoping that - you know, we had a lot of interest from different broadcasters around the world and we were hoping that we would get picked up. And so had I said yes to ['Stargate: Atlantis'], I would've basically killed 'Sanctuary' where it stood because I wouldn't have been available to do it, and it would've gone away."

Fans should know, however, that her moving on is not necessarily permanent since her character could pop up in the future. "'Stargate' was very gracious and understood my need to sort of move on. The fact that there was still the possibility of 'Stargate' movies and that I would definitely be involved in them made it sort of a soft landing because I wasn't actually saying good-bye. I was saying see you later."

With her new character of Dr. Helen Magnus, Tapping explained that she employed efforts to distance herself from her long-running "Stargate" character, including going from blonde to brunette. "When I first decided to do Helen Magnus it was a real conscious choice to have absolutely no vestige of Sam Carter in this character... everything from her appearance to her voice, to her walk, to her wardrobe, everything. I just felt in the end to completely reinvent. Partly as a woman, I just felt it was time and, as an actress, I just felt it was time to just try something completely different. And it's kind of great because I go places and people don't recognize me; people that I've worked with for ten years don't recognize me."

With all this attention to the appearance of Helen Magnus, one thing that should be mentioned is that the character also happens to be 157 years old, a point that is a mysterious story unto itself and will be revealed in an upcoming episode. Tapping joked that "[Helen] bathes in botox." Growing more serious, she teased, "Wait until the episode 'The Five' and you'll get the full meal deal on Helen Magnus and how she came to be who she is and why she's still around."

Tapping also expressed her gratitude for having the cable television platform to spread the "Sanctuary" story. "The beauty of being given a 13-episode arc for our first season is that we've been able to pull these stories out, like just create this huge mythology that we couldn't do in the two hours of webisodes. We sort of packed a lot into those two hours but now we're able to sort of draw that mythology out."

The difference in physicality of Helen Magnus was also a challenge for Tapping after having played her role in "Stargate" for so long. "Sam is so comfortable in her own skin and Helen is this very sexual, more mysterious being. She has a much darker edge to her and it was sort of [challenging] finding that because Carter always looks on the bright side and Helen has been around so long and has seen so much of the evil in human society, if you will."

Tapping also made a strong effort in nailing the perfect way she thought Helen would speak. "I wanted her voice to still have that carriage of the aristocrat and the use of proper English. But she's been around for so long that it couldn't be so highbrow. It still had to be sort of accessible to modern day vernaculars. So finding that was a challenge." There was one place off set that Tapping used to figure out the correct accent for Helen. "I walked around for days trying different accents on people, unwitting, ordering coffee at Starbucks as this mid-Atlantic wasn't working for me so I had to pull back. It was kind of goofy but that was part of the challenge and the joy of creating this new character."

An important element of the mythology of the series is the plethora of abnormal creatures that inhabit the Sanctuary. One way the series makes this new world relatable to viewers is to provide a regular character that is also seeing the Sanctuary for the first time. Tapping explains that Helen "pulls into the fray a young forensic psychiatrist named Will Zimmerman (Robin Dunne) who has always sort of thought outside the box and has therefore been shunned by regular law enforcement agencies but in fact now realizes that the things that he's sort of tried to investigate are now real. You're kind of seeing a lot of the Sanctuary and a lot of the creatures [and] mythologies through his eyes as sort of the everyman."

Another distinct component to the series is the extensive use of green screen to create the everyday environment that the characters inhabit, including the Sanctuary. Tapping estimated "about 70/30 [or] 75/25 is green screen to practical. We built some practical sets. Helen Magnus's office, for example, is for the most part a practical set except for the ceiling and what you see out the windows. But otherwise it is entirely virtual." Tapping likens acting with green screen is much like another acting platform. "It's like doing theater [and] you get used to it very quickly. David Geddes is our Director of Photography and he's literally an artist. He creates this palette for you where you believe there's a window with sunlight streaming in and you can tell what hour of day it is by the way he's lit it. So you get those visual cues and it makes it that much more real."

With such a massive use of visual effects, do the visual effects ever eclipse the narrative flow and characters in the series? "What's happening is really what's happening to the characters," Tapping said. "So the hard thing for the writers is sort of marrying more of our creatures and how to make that work because they're interacting with the actors. And that's the hard thing... it's not really just about the cool effect or what they look like. It's about what's at the heart of it. That sounds kind of hokey but it's true."

One manner in which Helen Magnus, for example, keeps her emotional core pulsing is in giving her a daughter and having mother/daughter issues exist as part of the mystery in the narrative. Trying her best to explain without giving too much away, Tapping carefully said, "I'm still trying to wrap my head around how to play this out but Helen made a choice to bring a child into the world knowing that she could possibly watch her grow old and die... not knowing if Ashley (played by Emilie Ullerup) has the same gift that Helen has... not knowing if Ashley will have the longevity." Given the sci-fi genre, however, the parent/child narrative staple finds itself in unfamiliar territory, Tapping added. "There [are] times when the mother/daughter dynamic flashes up and it sort of feels weird. It's like Ashley, be careful out there and yet you're sending her out to fight an invisible monster in the caves underneath the city."

"Sanctuary" premieres tonight on the Sci Fi Channel at 9:00/8:00c with a special two-hour episode before it settles into its regular Friday night at 10:00/9:00c one-hour slot next week.