This post is about the mythology, for the historical and cultural information, check out the post about the Danes.
Befitting their culture, the Norse have one of the most gruesome creation myths that I have personally come across. They believed that in the beginning, there were two worlds, Muspelheim and Niflheim, the first of fire and the second of ice. The air of the two worlds collided eventually collided and Ymir and the cow Audhumia were created. The gods sprang forth from the sweat of Ymir and the saliva of the cow. When the gods were strong and plentiful enough, they killed Ymir, and his blood flooded the world (another blood flood myth), killing most of the gods. They then created seven more worlds using his flesh, blood, and bones.
The nine worlds of the Norse existed on an immense tree, called Yggdrasill. A gigantic, vicious dragon is said to chew on its roots. The nine worlds, while never mentioned in one source together, are Asgard, Vanaheimer, Alfheimer, Midgard (our world), Jotunheimer, Niovellir, Muspell, Neflher, and Hel. Asgard can be reached by a rainbow bridge called Bifrost. Hel was where the dead who did not die in valor went. It was ruled over by the giantess, Hel. The heroes, and those who did die with valor went to either Valhalla or Folkvangr, both in Asgard. Valhalla was a great hall belonging to the god Odin, and Folkvrangr belonged to Freyja. Once there, the heroes prepare to help Odin when Ragnarok comes.
A Valkyrie is mythical woman who decided who decided who fell in battle. They would guide the fallen to the halls of Valhalla. They were also sometimes associated with ravens.
The god Loki was a trickster shapeshifter, and is the father of various Norse mythological creatures, includinf Hel, Fenrir, Jörmungandr, and Sleipnir (and horse similar to the Korean Chollima). When he killed the god Baldr, the gods bound Loki with the entrails of his son. He is also said to play a major part in Ragnarok.
Jormungandr is a giant serpent that encircles Midgard (the earth). He is also known as the World Serpent. Jormungandr fought Thor twice, and is prophesied to fight him a third time during Ragnarok.
Ragnarok is a series of events that will culminate with the death of many important Norse deities, and the submersion of the world. Eventually, the world will arise renewed and will be repopulated by the surviving gods and humans.
Book recommendations for reading challeges: