A star system in Tholian space in the mirror universe, where the Tholians held the captured USS Defiant in a drydock built inside a hollowed-out moon.
The Vintaak system appears in the two-part Enterprise episode In a Mirror, Darkly, which is set wholly in the mirror universe in 2155.
The Tholians have pulled the USS Defiant, a Constitution-class ship from the prime universe's future, through an interphasic rift. They keep it at a dock hidden in a moon in the Vintaak system, where slave workers are stripping it for its technology. Commander Archer takes over the ISS Enterprise and heads there to capture the ship for himself.
His boarding party gets the Defiant running, but the Tholians trap and destroy the ISS Enterprise in an energy web. The Defiant fights its way out, and Archer's team has to deal with the Gorn overseer Slar, who is still aboard.