Monograms originated in the classical world as producers’ marks, but their use became much more widespread in late antiquity, when they not only appeared in various new material media but also developed into more sophisticated and aesthetically appealing visual devices, encoding personal names and titles as well as various ritualistic phrases. This chapter surveys these newly acquired functions, turning them into liminal graphic devices and visual tokens of social power, as well as various messages conveyed by such monogrammatic devices. Since late antique and early medieval monograms communicated their linguistic and symbolic messages by means of a dual-coding system, they should be viewed in the context of this volume as phenomena situated in between hidden writing and semasiography.