Historically, mapmaking was a fairly imprecise task . . .to fill blank areas on the maps, mapmakers used to include textual/graphic warnings of the dangers of going into uncharted territory. Such warnings took the form of sea serpents, dragons, mythical and, sometimes, even real creatures. The actual line "Here There Be Dragons" has been found only once, on the 16th-century Lenox Globe — but is too cool to give up.
Cerberus or Kerberos, in Greek and Roman mythology, is a multi-headed hound (usually three-headed) which guards the gates of the Underworld, to prevent those who have crossed the river Styx from ever escaping.
Skogsrån (watchers of the forest) are mysterious women who guard the forest and all its creatures. Seen from the front they are unearthly beautiful, but their backs are hollow like old and rotten trees, and they often have the tail of an animal. To protect the forest, they seduce and sleep with woodcutters and then steal their souls, leaving them empty husks of their former selves.