When Scarlett and Bod enter the barrow grave for the first time, the Indigo Man appears to frighten them. Scarlett doesn’t have the Freedom of the Graveyard like Bod does, so the fact that even she can see the Indigo Man makes it clear that he isn’t a ghost. Instead, he’s a “scarecrow” designed to frighten would-be grave robbers. He looks like he’s been dead a long time and has purple-blue designs either tattooed or painted on his face.