Harry Turtledove The Breath of God
This is the second novel in the series The World Beyond. It was preceded by Beyond the Gap. The novel is a kind of fantasy setting, but it feels very different. The magic being described is not the magic of throwing lightning bolts and summoning strange creatures. It is often quite subtle. A person may start clucking like a chicken, or become much more afraid of mammoths, or be bedeviled by flies.
The ice wall separating the glacier from the Raumsdalian Empire is melting. A ruthless barbarian tribe called the "Rulers" is invading. They ride mammoths and practice dark magic. In the north of the empire the barbarian Bisogoths are being crushed and enslaved.
A wandering adventurer, Count Hamnet Thyssen and his companions, Ulric Skakki , a tribal leders referred to as his ferocity, and the shamaness Liv are running and fighting the "Rulers." They are also seeking "The Golden Shrine." Eventually they are forced to the top of the glacier where it is so stark that the people on top of the the glacier resort to cannibalism to survive.
Count Hamnet, the main character very much reminds me of the accounts of Sir Richard Burton, Ibn Battuta, or Lawrence of Arabia. He is a man more comfortable living among barbarians who herd mammoths and musk oxen than living at court. He is so hated by the emperor that he is thrown in the dungeon when he comes back to warn the emperor of Raumsdalia.
This novel reads like a cross between a mens adventure novel, a bit of an alternate history story, and a fantasy novel. It incorporates all three. There is lots of action, sex, fighting, and some rather crude jokes thrown in for good measure. Harry Turtledove writes alternative history and fantasy novels. His most famous novel is Guns of the South. My favorite novel by him is Fox and Empire.