Vostok. Erevos

It showed me something it had not yet learned the shape of. And I am afraid, now, that I taught it the rest. Lake Vostok is the oldest, largest, deepest lake on Earth, and the first door the thing behind Erevos and Concordia ever showed a human being, thirty-five years before Elin Kavanagh was told the story started. The Soviets found it in 1989. The Consortium has been quietly watching it ever since. Now Elin holds the only signature that matters: one that opens Vostok, or one that closes it forever.
Either way, she serves the machine that built her horror into its own PR. At the station, a new voice, glaciologist Vera Orlova, knows more about the array beneath the ice than she's been told to say. The Erevos series ends where it began: at the bottom of the world, with the oldest room in the house, and a species patient enough to wait thirty-five years for exactly this moment.