Short answers, pulled from the story.
Richard Wagner's Der Ring des Nibelungen is a four-opera cycle that begins with a dwarf named Alberich stealing stolen river gold from the Rhinemaidens to forge a ring of absolute power. This ring grants dominion over the entire world and sets in motion a chain of events spanning three generations of characters. The cycle concludes with a final cataclysm that destroys Valhalla and the divine order.
Richard Wagner wrote the libretto and music for this cycle over the course of twenty-six years from 1848 to 1874. He abandoned the work for twelve years to compose Tristan und Isolde before completing the four parts Das Rheingold, Die Walküre, Siegfried, and Götterdämmerung. The first performance as a cycle opened the first Bayreuth Festival in 1876, beginning with Das Rheingold on the 13th of August and ending with Götterdämmerung on the 17th of August.
Richard Wagner decided on a location in the Bavarian town of Bayreuth in 1871 and moved there in 1872 to construct a purpose-built theatre. King Ludwig II of Bavaria rescued the project in 1874 by donating the needed funds after Wagner spent two years attempting to raise capital with scant success. The Bayreuth Festspielhaus opened in 1876 with the first complete performance of the Ring cycle.
Wotan, the king of the gods and god of knowledge, is the central figure whose schemes to regain the ring drive much of the action in the story. The drama involves his mortal son Siegmund and his mortal daughter Sieglinde, who are the parents of the hero Siegfried. The plot also features Alberich, the demigod Loge, the giants Fafner and Fasolt, and Alberich's son Hagen who wants the ring for himself.
The 1976 centennial production of Richard Wagner's Der Ring des Nibelungen was directed by Patrice Chéreau and conducted by Pierre Boulez. Set in the Industrial Revolution, it replaced the depths of the Rhine with a hydroelectric power dam and featured grimy sets populated by men and gods in 19th and 20th century business suits. This production drew heavily on the reading of the Ring as a revolutionary drama and critique of the modern world and sold out its final performances in 1995.
The Metropolitan Opera performed the Robert Lepage production of Richard Wagner's Der Ring des Nibelungen for just shy of ten years with only three complete cycles having been given. The production was revived in 2019 for the first time since 2013 with Philippe Jordan conducting but was known to break down during earlier runs. The Met has confirmed that this controversial and expensive production will not return again and will be replaced by a new production in 2025.