ergosphere
The ergosphere is a region surrounding a rotating black hole, specifically a type known as a Kerr black hole. In this area, the intense gravitational pull and the rotation of the black hole cause spacetime to be dragged along with it. This effect allows objects within the ergosphere to gain energy and potentially escape the black hole's grasp, unlike those that cross the event horizon.
Inside the ergosphere, no object can remain stationary relative to a distant observer due to the extreme warping of spacetime. The boundary of the ergosphere is called the ergosurface, and it marks the limit where objects can still escape the black hole's influence while being affected by its rotation.