Hiisi originally denoted sacred places or groves, and only later came to mean demonic or trickster-like beings and various mythological entities. In later Finno-Karelian folklore it is tied to mountains and cliffs, woods and hills — outstanding features or rough terrain. Bound up with trolls and giants, in some tales the giants throw stones.
Its malevolent nature swelled as Finland was Christianized, and its name came to overlap with the Christian Devil. A primordial spirit of the land, older than humans and indifferent to them, later branded a demon, connects to our world’s register — the ancient thing called again under a new name.