They spoke Old Norse and they went into the iron age in 500 BC. They worshipped many different gods such as Odin, the king of the gods, Thor the god of thunder, Loki, the god of trickery and thieves, Balder, son of Odin, and Heimdall, the god of light. They also believed in Aegir, the Norse god of the sea and they believed in frost giants of the snow kingdom Jotunheim. They believed that the gods inhabited the kingdom of Asgard and they called Earth "Midgard".
Norse mythology also has similarities to Christianity. For example, Norse mythology explains the creation story of Midgard. The first humans were called Ask and Embla, but in the bible, they are Adam and Eve. Odin also sacrificed himself onto the world tree, Yggdrasil, similar to how Jesus was crucified by Romans. By the 1100's, the Norse had mostly been converted to Christians.