Addarion Bach, better known as Addario, was a dwarf from Coppertown, near Tretogor. He was a musician and played the horn in a miners' band. However, his very large family was from Cidaris and, in keeping with dwarven customs, was obligated to show up for every major event, like weddings and funerals, and thus he knew the roads from Redania to Cidaris perfectly.
On July 9, 1245, he was waiting at a post station in the Pontaria/Riverside region to catch the next mail coach in a couple days to make his way back home from yet another family event when Geralt, having gone through a bad portal, ended up in the region and came across the post station. Before they could really converse, the remains of Shevlov's free company showed up, not realizing Geralt was there, and the witcher and the group fought for a bit before Temerian soldiers approached, incidentally looking for the Redanian gang but not knowing what they looked like. Addario, a pacifist who hated to see anyone be hanged, passed the three gang members off as part of his company and both the soldiers and gang members soon left. However, on learning Geralt intended to get to Novigrad soon, Addario decided to go with him part of the trip, as he felt he'd be bored waiting and the fact that the female gang member gave him a look like she'd come back to kill him for calling her a whore earlier during the made-up alibi.
Addario led the way to a port in Wiaterna, though stopping for the night at Sylvan Dam to rest a bit and telling Geralt the story of how the Prophet Lebioda's skeletal remains were recovered. The following morning they soon arrive at Wiaterna and spot the Prophet Lebioda ship and, incidentally, its owner nearby chats with them about it.