Yan-Isleth
The Yan-Isleth, or Brotherhood of the Sword, was an elite Klingon division charged with protecting the Klingon chancellor. They guarded the chancellor at all times. 

In 2373, Worf cautioned his fellow  crew members that getting close to Gowron in order to prove that he was a Changeling would be difficult, given the Yan-Isleth's close watch on him. Jadzia Dax supplied the English translation of the term. Miles O'Brien doubted they could avoid the Brotherhood long enough to prove their suspicions. ()

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Klingonese
Klingon agencies