One really nice thing about writing fantasy or science fiction is that one can revisit the myths of old and give them new twists, or just steal a good story for your own needs. Either way, it can work out to be great fun. Here we have the fourth doctor, Tom Baker, foiling a vile alien who just happens to live in a maze and just happens to have bullish features. The story pretty much follows the line of the myths of old, with the additions of black holes, zap guns, and of course the Doctor.
One thing I love about the fourth Doctor stories are his companions. Not just the usual bunch of Doctor groupies along for the ride, they tended to be very capable characters in their own right. I've always enjoyed Romana most of all. Being a fellow Time Lord she could double speak techgoop as good as the Doctor, and she looked really good doing it.