A Voyage to Hyperborea: A Fantasy with Gill Slits (The Haliverse)

A Haliverse fantasy: Beneath Greenland's glaciers...
All Toby Gilman wants is a postdoc position where he can pursue his studies in ancient Arctic linguistics and keep the secret of his nonhuman ancestry safely hidden.
The bitter academic politics in his field leaves him only one option: a Miskatonic University expedition to an isolated station on the eastern coast of Greenland. The station needs a a linguist who can decipher the language of the long-vanished Hyperborean civilization.
Having no other choice, he sails with the advance party to the wilderness on Tornarssukalik Inlet. But the expedition is more than it seems, and he is not the only nonhuman among its members.
A lethal peril threatens the survival of Earth itself, and the Great Old Ones and their deadly enemies are both in motion…and they are not alone.
When disaster strikes Tornarssukalik Station, Toby must make his escape across arctic wasteland, sail on a ship crewed crewed by undead pirates and captained by the Terrible Old Man, and face all his deepest fears in a journey in which love, betrayal, and death are constant companions.
It is a journey that will end in the caverns far below Mount Voormithadreth, where the nightmare-being, Abhoth, guards secrets that could end the world...