Starfleet crew is assigned to manage it, led by Commander Benjamin Sisko. Shortly after his arrival, Sisko discovers a stable wormhole in Bajoran space between the Alpha Quadrant and the unexplored Gamma Quadrant, and the station is moved near the wormhole's entrance. The wormhole is the home of powerful, non-corporeal aliens whom the Bajorans worship as "the Prophets". Sisko is revered by the Bajorans as the Prophets' "Emissary"; although he is initially uncomfortable with being a religious figure, he gradually grows to accept his role. Deep Space Nine and Bajor quickly become a center for exploration, interstellar trade, political maneuvering, and finally open conflict. Threats come not only from Cardassians, Klingons and Romulans from the Alpha Quadrant, but later from the Dominion, a powerful empire in the Gamma Quadrant ruled by a race of shapeshifters. The starship USS Defiant is assigned to help protect the station. When the Dominion and the Cardassians take up arms against the Federation and its allies starting in the fifth season, Deep Space Nine becomes a key Federation base in the Dominion War. According to co-creator Berman, he and Piller considered setting the new series on a colony planet, but they decided a space station would appeal more to viewers, and would save the money required for a land-based show's on-location shooting. They did not want the show set aboard a starship because Star Trek: The Next Generation was still in production, and in Berman's words, it "seemed ridiculous to have two shows—two casts of characters—that were off going where no man has gone before". While its predecessors tended to restore the status quo ante at the end of each episode, allowing out-of-order viewing, DS9 contains story arcs that span episodes and seasons. One installment often builds upon earlier ones, with several cliffhanger endings. Michael Piller considered this one of the series' best qualities, allowing repercussions of past episodes to influence future events and forcing characters to "learn that actions have consequences." This trend was especially noticeable toward the series finale, by which time the show was intentionally scripted as a serial. Unlike Star Trek: The Next Generation, interpersonal conflicts were prominently featured in DS9. This was at the suggestion of Star Trek: The Next Generations writers, many of whom also wrote for DS9, who said that Roddenberry's prohibition of conflicts within the crew restricted their ability to write compelling dramatic stories. In Piller's words,