Isolytic subspace weapon

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An Isolytic subspace weapon is a type of metaweapon capable of mass destruction in a star system. The weapon functions by creating a tear in subspace, severely damaging everything in the area. In one case, the use of an isolytic subspace weapon by a Klingon ship resulted in the destruction of the Romulan planet Algeron III, leaving behind only the Algeron Effect (TLE novel: Serpents Among the Ruins)

In 2311, the United Federation of Planets, Romulan Star Empire, and Klingon Empire all formally banned the creation and use of isolytic subspace weapons during the Treaty of Algeron (TLE novel: Serpents Among the Ruins)

The Son'a were known to use these types of weapons onboard their warships. (TNG movie: Star Trek: Insurrection)

In December 2376, the Ascendants detonated an isolytic subspace weapon, causing a star near the Great Link's planet to go nova. The Progenitor was killed by the radiation. (DS9 novel: The Dominion: Olympus Descending)