Thor #337 CGC (9.0)

1st appearance of Beta Ray Bill, a Korbinite alien worthy of picking up Mjolnir

1st appearance of Lorelai, the sister of Enchantress

This is the beginning of the end. In the incrypt of Mjolnir says "Whosoever holds this hammer, if he be worthy, shall possess the power of Thor". Well, what happens when someone else is worthy too? This issue marks not just the beginning of the Walt Simonson era in Thor comic, also introduce great changes to the character.