also play an important role in Norse mythology. In Norse and German texts, dwarfs live in mountains and are known as great smiths and craftsmen. They may have originally been nature spirits or demons of death. Snorri Sturluson equates the dwarfs to a subgroup of the elves, and many high medieval German epics and some Old Norse myths give dwarfs names with the word or ("elf") in them, suggesting some confusion between the two. However, there is no evidence that the dwarfs were worshiped. In Anglo-Saxon England, dwarfs were potentially dangerous supernatural beings associated with madness, fever, and dementia, and have no known association with mountains. Dragons occur in Germanic mythology, with Norse examples including Níðhöggr and the world-serpent Jörmungandr. It is difficult to tell how much existing sources have been influenced by Greco-Roman and Christian ideas about dragons. Based on the native word (, related to , "snake"), the early description in Beowulf, and early pictorial depictions, they were probably imagined as snake-like and of large size, able to spit poison or fire, and dwelled under the earth. Some dragons are described as crawling, while others are said to be able to fly. Pantheon Due to the scarcity of sources and the origin of the Germanic gods over a broad period of time and in different locations, it is not possible to reconstruct a full pantheon of Germanic deities that is valid for Germanic religion everywhere; this is only possible for the last stage of Germanic religion, Norse paganism. People in different times and places would have worshiped different individual gods and groups of gods. Placename evidence containing divine names gives some indication of which gods were important in particular regions, however, such names are not well attested or researched outside Scandinavia. The following section first includes some information on the gods attested during the Roman period, then the four main Germanic gods *Tiwaz (Tyr), Thunraz (Thor), *Wodanaz (Odin), and Frijjō (Frigg), who are securely attested since the early Middle Ages but were probably worshiped during Roman times, and finally some information on other gods, many of whom are only attested in Norse paganism. Roman-era Germanic gods with Roman names The Roman authors Julius Caesar and Tacitus both use Roman names to describe foreign gods, but whereas Caesar claims the Germani worshiped no individual gods but only natural phenomena such as the sun, moon, and fire, Tacitus mentions a