The Sci Fi Channel has added two more actors to its upcoming high-profile pilots.

Polly Walker has joined the cast of the "Battlestar Galactica" prequel "Caprica," while Saul Rubinek has come on board "Warehouse 13," according to The Hollywood Reporter.

In the world of "Caprica," set 50 years before "BSG," two rival families -- the Graystones and the Adamas -- grow, compete, and thrive in the vibrant world of the 12 Colonies. Walker will play Sister Clarice Willow, the duplicitous high priestess at the private religious school, Athena Academy, that some of the younger main characters attend. She's also a key figure in the single-god underground religious group.

Walker joins Esai Morales, who plays Joseph Adama, Eric Stoltz, who plays computer engineer Daniel Graystone, Alessandra Toressani as his daughter Zoe and Paul Malcolmson, who plays a double agent/surgeon.

Meanwhile, Rubinek has been cast as Artie Nielsen, the Secret Service agent in charge of the "Warehouse 13" in South Dakota where the the U.S. government has deposited all of the strange artifacts, relics and supernatural objects it's stumbled across over the centuries. He joins leads Joanne Kelly and Eddie McClintock, the FBI agents who have to keep an eye on the stuff and track down anything that has gone missing.

Rubinek has an extensive film resume that includes "Unforgiven," "True Romance," "The Family Man" and "Rush Hour 2." He's also guest starred on "Curb Your Enthusiasm," "Eureka" and "Psych."

Walker is a British actress known for the HBO series "Rome" and the short-lived "Cane."