The Serpent Crown is a fictional item in the Marvel universe which first appeared in 1968 (as the Helmet of Power) in issue #101 of the 1st volume of the Tales to Astonish comic book series. It made its first appearance as the "Serpent Crown" in 1969 in issue #9 of the 1st volume of the Sub-Mariner comic book series.
The Serpent Crown (aka, the Helmet of Power, Crown of Lemuria, Helmet of the Ancients, and Seven-Headed Serpent Crown of Lost Lemuria) are mystical artifacts created by mortals, per the instructions sent to them by Set, an Old One. They grant men a variety of powers but serve as tools for Set to control those individuals.
The powers which men receive vary depending on the individual. Which have included mind reading, hypnosis, mental manipulation of matter & energy (e.g. creating earthquakes), superhuman strength & endurance, creating illusions, levitation, communication with others wearing the Serpent Crown (including those in other dimensions), and powerful destructive mystical bolts.