Vikor was Mark Taylor's sketch. And while Roger Sweet did sort of design the guy we call Vykron, my understanding is that Taylor actually designed the harness, which is the only thing about Vykron that is really recognizably He-Man. I believe Taylor is correct that he came up with the name He-Man.
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Regarding Goddess/Teela, they were originally separate characters. The Goddess was human with a greet suit, not unlike Man-At-Arms. Her face was originally flesh colored. As imagined by Mark Taylor, she was originally bad, but then became a guardian of Grayskull (a lot of characters originally designed as bad or good later switched sides - like Zodac, Mer-Man, Tri-Klops, Stratos).
I believe they consolidated Goddess (actually her name was Sorceress) and Teela into the same person because they didn't want to put out two female toys early in the line. So Teela got the snake armor.