Epic Journeys II

I listed several epic journeys in Poul Anderson's works here and have just found another:

the Inuit tribe gathers in an oppressively hot house;
the angakok (shaman) strips naked and lies on a bearskin on a ledge where he is bound with thongs;
the lamps are extinguished except for one tiny flame;
the angakok chants rhythmically to the beat of a drum;
the people sing, sway, writhe, speak in tongues, howl and scream;
the angakok enters a trance (or disappears physically but in the dark?);
he -
- swims down through the rock;
enters the underworld;
goes out under the waters;
passes the country of the dead and an abyss with an eternally whirling disc of ice and a boiling cauldron of seals;
evades a baying, snapping guardian dog greater than a bear;
crosses a bottomless chasm on a knife-thin bridge;
comes before huge, one-eyed, hostile Sedna, Mother of the Sea;
compels her to divulge undersea intelligence;
returns when the single flame has been extinguished;
prophesies for the tribe;
tells the merfolk where their kin have gone, using coastal place names unfamiliar to him that Sedna has learned from drowned sailors.