The Penrose Process

When you have a rotating black hole, it's able to spin the space time around it. And because this dragging of space time extends beyond the event horizon, it essentially can insert energy into the universe around it. It also makes the math a whole lot uglier. Even in graduate school, most of the time when you're doing the maths, they tell you to assume a non rotating black hole,. Because they show a small moderatum of kindness, right?