Comic dated June 10, 1964
Here we have the introduction of Mr. Hyde in the A-story and the B-story (When Heimdall Failed) is an archetypal Kirby fever dream – in a good way. Heimdall suspects foul play when a tiny air sprite (a Vanna) sneaks past him. He considers this a failure, but Odin praises him for giving Asgard advance warning based on his instincts.
Mr. Hyde will probably be back again and again. (What is this “probably”? It’s Marvel comics! Every last inch of the early stuff has been repeatedly strip-mined for content.)
Just in case you’re curious about the length in these two-story anthology books, the main tale gets 18 pages and the back-up story gets five. This is less balanced than the contemporary Marvel anthologies where two top-level stars share billing; page counts tend to be more evenly split there.