To truly understand any mythology you must get rid of what you think you know, for one Loki is not the Thors brother he's actually Odin's blood brother. For the most part the movies on Norse mythology are completely inaccurate.
Ragnarok is the cataclysmic destruction of the cosmos and everything in it – even the gods. Someday – whenever the Norns decree it – there shall come a Great Winter. Mankind will become so desperate for food and other necessities of life that all laws and morals will fall away.The following battles will be fought:
Baldr, Hod, Hoenir, Magni, Modi, Njord, Vidar, Vali and the daughter of Sol are stated to survive Ragnarok. Vidar (who avenges Odin) and Vali who where unharmed by Surtr fire or the flood. Magni and Modi who will wield their father's(Thor) hammer, Mjolnir, will also live. Njord is stated to return to Vanaheim at "the doom of man" which has been interpreted as Ragnarok, Sol(who dies) gives birth to a daughter who follow her path in the new world.