Known directly from a single inscription and image at Neumagen, Germany where he is equated with and depicted as Mercury. He is the consort of Rosmerta. He, therefore, is the male component of the 'divine couple' portrayed throughout Gaul and southern Britain.

Though little is known directly about this deity an image of him can be generated as he represents the 'Mercury' aspect of the divine Rosmertan couple. This god is often depicted with a caduceus in his left hand and a cockerel by his right side; the caduceus, of course, being the heraldic staff of Mercury, associated with healing powers and his role as a psychopomp (leading souls to the netherworld); whereas the cockerel is a Chthonic attribute (ie relating to the netherworld) which indicates that Abgatiacus himself might have been a psychopomp. His rôle being to guide the guide the souls of the departed to the netherworld.

His consort, Rosmerta, is known throughout all of the Brythonic world, from Romania, Germany, Luxembourg, France and Britain where she is always depicted with a Mars-type figure. Thus it may be that the cult of this deity was far more widespread than generally believed. I suggest that the deity's name may be derived from the proto-Celtic roots *ab/abon (river) and the Gaulish gabi (to take, to hold) with the deific word-ending us/acus giving: 'He who holds the waters' which would be a fitting epithet for a healing deity.