("The Twilight the Gods"), Royal Opera House, Covent Garden. Siegfried, disguised the Tarnhelm as Gunther, has brought Brunnhilde from her rock to be Gunther’s bride, and is himself to be wedded to Gutrune. Brunnhilde accuses him of treachery, and they swear on Hagen’s spear. Brunnhilde. Overwhelmed by her betrayal, persuades Hagen and his men to slay Siegfried, telling him that only in the back is he vulnerable. All this tragedy is only the inevitable fulfilment of the curse on the ring