I'm gonna try to sum the important things up in a nutshell.
Satma appears only in #34 of the German audio plays.
He is the ruler of the Hyperspace. He resides in a fortress that looks almost like Grayskull, but with horns, and commands warriors more gruesome than even Skeletor's Evil Warriors. Interesting is that Satma motivates his warriors by promising them gold.
Satma's appearance actually isn't explained much at all. When seeing him first, Man-At-Arms mistakes him to be Skeletor. He-Man then corrects him, stating that he "looks like Skeletor, but he's not". To which Orko adds that "he has two horns... he's the devil!". Maybe the name Satma actually might have been a tweak from "Satan" by the author. Because of that, I have sort of an issue with the picture from the .org poll - it's merely one fan interpretation, just as this one is:
Satma's figure could come with Icebird and the Power Sword of Evil. It's weapon whose blade is clad in "hyperspace ice". Said weapon plays a crucial role, when Dragstor brings it to Skeletor in episode #33. Skeletor hits He-Man slightly with the sword, to which He-Man then falls into a nigh-dead shape. Icebird is made from hyperspace ice and has the ability to teleport into Hyperspace. In #33, he teleports Buzz-Off and Moss Man, and later He-Mans power sword into Hyperspace. That's the reason why the heroes go into Hyperspace in #34. Many German fans already regard Nepthu's Diamond Zoar as their Icebird.