With Anna's help, Elsa unfreezes and rides Nokk to save Arendelle from utter destruction. Spirits return fire, wind, and earth back to normal. Elsa had ventured too deeply into Ahtohallan and "drowned." Anna led the earth giants to the dam and provoked them into destroying it with their boulders almost losing her own life in the process. Anna did this believing that Arendelle would be absolutely destroyed by the water released by the dam.
Seriously, Nokk is one fast "horse" because it and Elsa made it to Arendelle despite being miles to the north of the dam and Arendelle. Next up, The Belmont Stakes, Preakness and The Kentucky Derby LOL...