(covers information from several alternate timelines)
Sto-vo-kor (also written Sto'Vo'Kor, or Suto'vo'qor in the Klingon language) was, in Klingon mythology, the afterlife for the honored dead, where all true warriors went after they died to fight an eternal battle against great enemies. The halls of Sto-vo-kor were said to be guarded by Kahless the Unforgettable. The dishonored dead, by contrast, were ferried on the Barge of the Dead to Gre'thor.
According to the ancient tradition of ak'voh, whenever a warrior died in battle, others stayed with the body to keep away predators, allowing the spirit to leave the body and go to Sto-Vo-Kor. (DS9: "The Ship")
Klingons could enter Sto-vo-kor by dying in battle or while performing a heroic deed. In addition, they could enter Sto-Vo-kor by allowing themselves to be killed by another Klingon. (DS9: "Children of Time", "Covenant")
Alternatively, in the event of a warrior dying as the result of a surprise attack or some other demise that lacks true honor, the relatives of the deceased could also perform such a deed in the name of the fallen to ensure their arrival in the halls, showing that the deceased has lived a life capable of inspiring others to great feats of courage. (DS9: "Image in the Sand", "Shadows and Symbols")
In 2151, after being told by Captain Jonathan Archer that a group of Xyrillians had been hiding in his ship's plasma wake and disrupting a number of systems, Captain Vorok declared that he was "more than willing to hasten their journey to Sto-vo-kor." (ENT: "Unexpected")
On Gaia in 2373, Brota believed that he would not take his place among the honored dead in Sto-vo-kor once the USS Defiant had departed, and the timeline he had been born into was erased. He considered it would have been a death 'unworthy' of entry into the afterlife. (DS9: "Children of Time")
Later that year, Kor wished Worf well and that they would see each other again in Sto-vo-kor after Kor believed he would die fighting the Dominion aboard the IKS Ning'tao. He also told Worf (after knocking him unconscious) that he would find Jadzia there and remind her of Worf's love. (DS9: "Once More Unto the Breach")