There have been notable warrior characters before, especially in the Classic Series. The Sontarans tend to be seen as the pinnacle of these and overshadow most of the others. It probably wasn't certain that the Sycorax, another warrior race, would stand out, but they managed it as the antagonists of the first Christmas Special of the revival. A big part of their appeal is their striking design. The bone helmets and ornate red cloaks are really visually interesting. Even with the masks off, their bony faces and red skin work to leave a memorable image. As with the Teller, it's a huge credit to the costume team. It's not just the physical design that made the Sycorax work so well. There were multiple hints of a deeper, interesting lore behind the Sycorax, from the use of blood control to the hisses about witchcraft when the Doctor regrew his hand. Even what was on screen was really well developed. The Sycorax leader was a subtly three-dimensional villain - prideful, devious and with a weird sense of honour. All in all, it's not hard to see why the Sycorax constantly feature on lists of aliens that should return.
