A container made by the long-dead Slaver Empire inside which time does not pass, so that objects sealed a billion years ago emerge unchanged.
Stasis boxes appear in the episode The Slaver Weapon, written by Larry Niven and drawing on his own fiction. They are the only relics of the Slavers, who ruled most of the galaxy a billion years ago until a war wiped out nearly all intelligent life.
The boxes are extremely rare and their contents have changed civilisations; one is said to have given Starfleet a vital advance in gravity technology. Each box can detect another.
Spock, Sulu and Uhura are carrying one aboard the shuttlecraft Copernicus when it reacts to a second on an ice planet in the Beta Lyrae system. That signal is bait laid by Kzinti raiders with an empty box, who seize the full one in the hope that it holds a weapon.