Knightfall stars Tom Cullen and focuses on the politics surrounding the Knights Templar, known for being infamously secretive and protective about Christianity's relics. Hamill will play Talus, a Knight Templar who is a veteran Crusader and who trains new members.
The show has performed well, currently being ranked third in cable dramas.
Eli Lehrer, History's EVP Programming, said, "In the face of ever-increasing competition, we're proud of History's track record of producing signature drama series that are epic in scope with complex characters. Whether it's the legendary Knights Templar, the extraordinary tale of medieval Norsemen, or the story of a formerly classified the United States Air Force program investigating UFOs during the Cold War, these series reflect our commitment to bringing the defining, big canvas stories of history to life. We look forward to offering our viewers a grittier, darker Knightfall in season two and welcoming Mark to the cast."