An honorific given by Klingons to their greatest and most seasoned warriors, borne above all by Kor, the old adversary of Kirk who reappears in Deep Space Nine.
Dahar Master is a title of the highest respect in the Klingon Empire. It is given to a handful of warriors whose deeds over a long life have become the stuff of song, and younger Klingons treat its holders with something close to awe.
The title is introduced in the Deep Space Nine episode Blood Oath, which brings back Kor, Koloth and Kang from the Original Series as old men bound to hunt down the Albino. It is most closely tied to Kor. Worf greets him as a Dahar Master in The Sword of Kahless and is overjoyed to join his quest.
In Once More Unto the Breach the title cannot win Kor a command, because General Martok still resents the day Kor blocked his entry into the officer class. Kor ends by proving the legend true, dying in a rearguard action against the Jem'Hadar.