Question: What video game published by Sierra Entertainment includes an antagonist figure who's mystery is the core of the series? 
Related documents: [0]  [DOC] F.E.A.R. First Encounter Assault Recon is a survival horror first-person shooter video game developed by Monolith Productions and published by Sierra Entertainment. It was released on October 17, 2005, for Microsoft Windows, and ported by Day 1 Studios to the Xbox 360 and PlayStation 3. TimeGate Studios has released two expansion packs, "F.E.A.R. Extraction Point" in October 2006, and "F.E.A.R. Perseus Mandate" in November 2007. A direct sequel titled "", was released in February 2009, and a second sequel, "F.3.A.R.", was released in June 2011, though it was developed by Day 1 Studios (now known as Wargaming Chicago-Baltimore), not by Monolith Productions. [END] 
[1]  [DOC] Alma Wade is a major antagonist and key figure in the "F.E.A.R." series of first-person shooter horror video games by Monolith Productions, introduced in "F.E.A.R." in 2005. The mystery of Alma is the very core of the series. [END] 
Answer: 
F.E.A.R.
F.E.A.R.