UPDATE 19/01/2016 8.20pm: The Baba Yaga: The Temple of the Witch DLC will indeed launch with the PC version, Square Enix has confirmed to Eurogamer.
ORIGINAL STORY 19/01/2016 6.03pm: Rise of the Tomb Raider's first story DLC expansion, Baba Yaga: The Temple of the Witch, is due on 26th January.
As reported by Polygon, it's unclear if this DLC will be available for Rise of the Tomb Raider's PC launch only a couple of days later on 28th January. We've requested comment from publisher Square Enix on that and will update should we gain clarification on the matter.
Baba Yaga: Temple of the Witch places Lara in a forest presided over by the mythical Baba Yaga, a creature from Slavic folklore that lives in a cottage set atop a pair of giant chicken legs. It should add "hours of new gameplay" and is included in a Season Pass.
Rise of the Tomb Raider's previous DLC was Endurance Mode, a score-attack challenge based on surviving the elements for as long as possible. A third piece of DLC entitled Cold Darkness Awakened will offer wave-based survival challenges.