The Finnish word for demon mentioned in the Kalevala. They are personifications of evil associated with woods, streams, and hills. There is a chief Hiisi who is aided by a number of lesser demons called hiiet within the Kalevala.
Poems 13-14 tells of Lemminkaeinen's attempt at pursuing Hiisi's elk. The elk escapes capture and curses Lemminkaeinen. Lemminkaeinen finally is able to capture the elk after a struggle and drive him to the North Farm. (From here)