The story opens with a flashback to young Thor, still looking forward to the day when he is worthy enough to wield the mystic Uru hammer Mjolnir. Failing to lift it yet once more, he chooses to take the ax Jarnborn on his journeys….
893 A.D.: Thor leads a Viking ship on a voyage to plunder what is now Russia. As they cross the fog-shrouded sea they spy a cloaked figure through the mist, walking on the water. The figure also spies them and flies in their wake….
Three days later along the Neva River, Thor and the Vikings are facing the Slavs in battle. The natives summon their gods and a white winged horse arrives—splattered with the blood of its missing rider. The Thunder God mounts the winged steed and heads into the sky to investigate and passes another flying horse, back this time and bearing the headless corpse of its rider. The corpse-like Gorr the God Butcher suddenly appears alongside and slashes the head off of Thor’s mount. The Thunder God plummets and lands astride the black horse and whirls to face his enemy. They battle in the sky while Thor recalls his meeting with a murderous rogue Asgardian god who terrified him utterly. Gorr, veteran at killing gods, beats Thor mercilessly, taunting him and demanding to know what Thor is a deity of; the hero whispers "Thunder" and a lighting strike crashes down, hurling them both to the Earth….
In the present day, Thor slays the God Butcher’s Black Berserker after a battle lasting several hours. He swears to avenge the slaughtered gods of Indigarr, no matter how long it takes.
Meanwhile, in the past, Thor lay very still in a snowy crater….