Thor: Ragnarok — Roy Thomas

The menace of Loki! The attack of the massive Midgard Serpent! The death of Balder! The sacrifice of Odin! Deadly battles with trolls and giants! The debut of a new redheaded Thor! All-out war with the forces of Hela! Does the fate of Asgard lie in the hands of a human reporter? As Ragnarok, the end of all the gods, looms on the horizon, Thor and allies Sif, Odin and the Warriors Three do all they can to stop it-but even their best may not be enough!

Collecting:

Thor (1966) #272-278; Prelude to Eternals Saga TPBs