Gods and Goddesses: For a very long time, the Vikings believed in many gods and goddesses. These stories are called Norse myths. Most Vikings believed that a warrior killed in battle would spend their afterlife in wonderful Valharra, where they were honored for all time, or at least until the final battle that would end the world.
Christianity: Some Vikings adopted Christianity, and found the belief in gods and goddesses to be old fashioned.
Monsters: For a very long time, the Vikings believed in monsters and mythical creatures like trolls, witches, shapeshifters, sorcerers, and ghosts. Even after some Vikings adopted Christianity, most still believed that giants, trolls, goblins, and other mythical creatures inhabited Middle Earth.
Good Luck Talismans: Most Vikings believed in good luck talismans. They carried good luck charms with them everywhere. Some talismans protected the Vikings from certain monsters.
Runes: Most Vikings believed that their alphabet, the Runes, was made of more than letters. They believed each letter had magical powers. One of the reasons they did not write things down that often was that they were careful that the power of the Runes did not fall into the wrong hands. Another reason, and possibly the real reason, is that the Vikings did not use ink. They carved each letter, and that took a lot of time. Written messages were very short.