Gravity well

There were naturally occurring gravity wells on Archetryx. (PROSE: The Apocalypse Element)

On Mars, a decaying segment of the Key to Time was disguised as the capstone of a pyramid. When Zara converted it to its true form, a gravity well was created that caused earthquakes and hurricanes for three decades. This devastated the civilization of the Ice Warriors. (AUDIO: The Judgement of Isskar)