It's just a model that appeared in Beta, but not anymore. We were left with its death animation and its portrait, though, and the base SD model in the campaign. Why? Because wc3 Reforged was not finished.
But fear no more, the model is fixed. I had to fix the decay visibility and this and that, but the model is now 100% functional.
Best of all? if you "replace" the model in your retail folder, you'll see the actual HD model in the campaign. So, I recommend importing this even if you are not going to use it.
You only need the main model, the portrait is already there and working (although it's ugly as hell), but if you want to include it in your custom maps, I'll upload both files for you.