Panthor is Skeletor's trusty feline steed. Basically he's just a purple flocked Battle Cat (which in turn was a panther borrowed from the earlier Mattel line, "Big Jim.")
Although I recently reacquired this specific one from a garage sale, I did have Panthor when I was a kid. My parents had gone to Vegas for a weekend trip and brought him back for me.
I always wondered if they just swung by the local toy store on the way home - "uh oh, we forgot to get the kids something!" - or if he was actually purchased while in Vegas, but I didn't really care. Panthor and Skeletor beat the "Mom and Dad went to Vegas and all I got was this lousy T-Shirt" shirt my sister and I usually got form my parents' trips to Vegas. Although I'm sure my parents got a big kick out of those shirts.
This is an original Skeletor, which also came in the garage sale lot I found this past summer.
He's missing his loin cloth or whatever you'd call that thing.
Seriously, what's cooler than a blue skinned, skull faced barbarian riding a purple Panther? In the eyes of a seven year old, not much.
Panthor's saddle is also just a green version of Battle Cat's saddle. I always wondered why they skimped out and didn't include a green helmet, but then again Panthor is evil, so he's not likely to adhere to the helmet laws of Eternia anyways.
I have a complete commemorative Skeletor figure from the early 2000s too...
...and you can see some differences, including the face sculpt (the original Skeletor is on the left.)
The plastic of the armor is also thinner/more translucent on the original Skeletor.
"I am the REAL Skeletor!"
Here's another shot of the commemorative Skeletor, with all his accessories.
"Greyskull shall be MINE! Haaahahahahhahaaaaaa!"
On a related note, a new era in Masters of the universe toys is about to begin with Mattel's online exclusive Masters of the Universe Classics series. I'm really looking forward to these new figures. Skeletor was recently previewed in ToyFare magazine and he looks great in the new/old style!