Who is Kora from The Descent: A Novel and what is their importance?

Kora is Ike's lover. She is described as a kind, gentle woman, who also enjoys mountain climbing. When Kora learns that she is pregnant, rather than tell Ike, she decides she must leave him to provide a more conventional life for their child. Before she can do this, however, Kora is captured by Isaac, a hadal, who takes her into the bowels of the earth and makes her his lover. The child is born and is raised by Isaac as a hadal. Kora dies an unexplained death, but it is clear to the reader that Kora was a strong woman who survived a significant amount of time among the hadals and was deeply loved by Ike and Isaac both.