One of the most ingenious aspects of Shada is the concept of an invisible spaceship as created by Douglas Adams. It's a set designer's dream, really, and it could be seen as an easy way out of an expensive situation.
But an invisible spaceship is easily the best way for an alien to hide somewhere. It's such a good idea that it's been used at least twice since Shada - in the 1986 film Star Trek IV: The Voyage Home, and again in Doctor Who in the 2007 story Human Nature/The Family of Blood.
However, it's what visible that is the highlight of this episode - Skagra's costume. If ever the phrase "space pimp" could ever be applied to anyone, it would be applied to Skagra. With a flowing cape and truly bombastic hat, Skagra is one the more outlandishly cool looking villains in Doctor Who, and holds his own, in a more futuristic sense, with the previously style king in Season 17, Count Scarlioni from City of Death.