Black hole drives were electrical drives that generated power with black holes. They were dangerous because the containment fields surrounding the black holes were extremely susceptible to sonic pulses. Because of this, they were banned in "every corner of the Seven Systems".
A group of Skinks used a black hole drive in their spaceship when they blockaded Vourakis 3. The Twelfth Doctor used his sonic sunglasses to break the drive's containment field and the ship was destroyed by the black hole. (COMIC: Pirates of Vourakis)
