The Messenger is one of Jason's men and so formerly of Medea's household. He is, therefore, somewhat sympathetic to her wishes and needs. His main function is to relate the gruesome events that took place at the palace in vivid detail after Medea's plot to kill the Princess and Creon is successful.
The timeline below shows where the character The Messenger appears in Medea. The colored dots and icons indicate which themes are associated with that appearance.