The Zurav Nebula was a stellar phenomena, a nebular gas cloud within Klingon Empire space, somewhere in the galaxy's Alpha and Beta Quadrants. In the year 2379, Chancellor Martok assembled a Klingon Defense Force fleet in the nebula under the command of Captain Logaar to launch a preemptive strike against the Tezwans, who had recently threatened the Klingon colony on QiV'ol.
When that fleet was destroyed over planet Tezwa by Federation-built nadion-pulse cannons and Starfleet observed an invasion force leaving Qo'noS to conquer the planet, there was a strong possibility that an unknown number of cloaked ships would from there join the original twenty ships. In the end, over sixty ships were disabled over Tezwa, among them the lead ship IKS veScharg'a and the IKS Ya'Vang. (TNG - A Time to... novel: A Time to Kill)