Journey Into Mystery #85 (Aug 1962) begins to build out Thor’s mythology by introducing Asgard, the rainbow bridge Bifrost, and Thor’s biggest nemesis: Loki, god of mischief. Poor Loki has been trapped in a tree until someone sheds a tear. Along comes ol’ Heimdall, Bifrost’s Warder, and Loki is able to manipulate one of his tear’s leaves to tickle Heimdall’s eye, causing a tear to be shed. Loki is free!
Loki wastes no time in discovering that Thor is on Earth, so he disguises himself in modern clothes and then causes a spectacle by color-inverting some people on the street. Naturally Doctor Don Blake and Jane Foster just happens to be in the crowd, so Loki is successful in flushing Thor out.
It takes a little prodding, but after Loki removes his disguise, Thor recognizes Loki, which is the first evidence that the Thor persona is not just a physical shell that the human Don Blake wears, but perhaps something more.
Loki successfully hypnotizes Thor, but then makes the rookie mistake of demanding Thor hand over his enchanted hammer. Thor recalls further memories that Odin, the rule of the Norse gods, has made certain that the hammer can never be “wrested from Thor”.
What happens next is a pretty good fight throughout the city, with Loki pulling some tricks and Thor overcoming them. Eventually Loki falls into the harbor and Thor remembers that Loki’s powers are nullified in water, so he saves him, and then quickly sends him back to Asgard using his hammer. We get a back-of-the-head shot of Odin, Balder, and Tyr as Loki arrives.
The final shot is of Donald Blake and Jane Foster walking the streets of the city. The writers try to set up a bit of a weird love triangle with Jane mooning over both Thor and Loki, but it basically falls a little flat.
Bring on my Asgard mythology!