Klingon planet on the Romulan border that has twice played a pivotal role in Alpha Quadrant history in the last century: in 2293, as the site of historic multi-planet Federation peace talks with the Klingons that were almost disrupted by the assassination of the UFP president, and in 2344 with the infamous Romulan massacre of the 4,000 Klingon outpost colonists there, engineered by the traitor Ja'rod, while the Romulan-Klingon alliance was still technically in effect.
For many years, Worf was thought to be the only survivor as a boy of six, but in 2366 his nurse, Kahlest, and younger brother Kurn, who was not present, were also discovered. The brothers' father and Ja'rod's rival, Mogh, was originally accused of betraying the colony's defense shield access codes, but it is Ja'rod's son Duras who had the "captured" files doctored as part of a cover-up, fostered by the High Council to avoid civil war if the truth got out.
In 2369, Worf discovered even more Klingons who had been captured while unconscious at a perimeter post, taken and held against their will, and dishonored by their choice of captivity over suicide. They opted stay in a secret Romulan camp on Carraya IV to avoid bringing dishonor to their families back home.