Animals appear as an omen by their appearance and activity through a symbolic message. The type of animal and their activity is the substance of the message. On the eve of his battle with Sir Mordred, King Arthur dreamt of being devoured by serpents, dragons, and other water beasts. The serpents and dragons alone mean great troubles within the land. Another example of an omen is Deirdre's dream of the three great birds.
Shape changing is another theme generally involving animals.
Sometimes humans are changed into the shape of other humans. Merlin, King Uther Pendragon, Pwyll, and King Arawn are examples. However, the forms changed into are most often those of animals. MacCulloch and Davidson make several references to people being changed into animals as punishment . This happens in the story Math Son of Mathonwy .