“The Nagus” is episode eleven of season one of Star Trek: Deep Space Nine.
The Grand Nagus, the ruler of the Ferengi, is visiting DS9. Quark is worried, because the Nagus could make a poor offer on his bar, and he would have no choice but to accept.
The Nagus wants to borrow Quark’s bar in order to have a meeting of the wealthiest Ferengi to discuss the matter of the Gamma Quadrant. The Ferengi have managed to acquire a bad reputation in the Alpha Quadrant, and the prospect of many new worlds that aren’t contaminated by that reputation is too big an opportunity to miss.
At the meeting, the Nagus announces something else. He’s going to be stepping down, and announces Quark as his successor. Quark is initially pleased, but discovers being the ruler of a bunch of cut-throat – sometimes literally – businessmen is not a particularly safe profession. Even worse, shortly after stepping down, the Nagus himself dies of natural causes, leaving Quark with no other options.