Mister Maxivermis Mind first appeared in Faucett Comics in 1943 in “Captain Marvel Adventures” #26 and reappeared in DC Comics in 1973. (As you may know or have gathered from the joke in the film, Captain Marvel used to be Shazam’s name.)
Mister Mind is a tiny worm/caterpillar creature from Venus. (He looks like a caterpillar but is classified as a Venusian worm. Don’t worry about the semantics. He’s a talking insect, friends.) When he began, he was an evil worm with glasses and a little box on his neck that allowed him to use human speech. You can see it on him in the first film, and it’s clearly causing his mechanical voice.
He’s a genius with the power of telepathy, telekinesis, hypnotism, and magic, and he’s a part of The Monster Society of Evil (one of the first comic book teams of villains). He can also quickly create powerfully strong silk cocoons. Mister Mind was sentenced and put to death by electrocution for working with the Nazis in the Fawcett Comics run, but somehow
Palpatine Mister Mind came back. Later on, he evolved into Hyperfly who can eat both time and space. I mean, caterpillars eat a lot, but dang.
When he showed up in DC Comics’ New 52, he forced Shazam to do a spell that unlocks and destroys the Seven Magiclands, which is what he may have been referring to in the first “Shazam!” film.