The chief literary source is Bede, a Christian monk who wrote of the old English calendar in his "De Temporum Ratione". Only a little Old English poetry has survived, and all of it has had Christian editors. The epic poem "Beowulf" is an important source of Anglo-Saxon pagan poetry and history, but it is clearly addressed to a Christian audience, containing numerous references to the Christian God, and using Christian phrasing and metaphor. The monster Grendel, for example, is described as a descendant of the biblical Cain. In fact, the only fragment of poetry dating to the pagan era that has not undergone edits by Christian editors is the "Finnsburgh Fragment".