Bart is a rock troll who once guarded camels for a Zerrikanian merchant, until Sigismund Dijkstra won him in a card game. He followed his new master north, and he is as loyal as he is large. Once, to save Dandelion from a ship bound for Kovir, Bart simply waded into a shallow stretch of the Pontar so the ship would run into his head and spring a leak. It worked.

In The Witcher 3

Bart guards Dijkstra’s “members-only savings club”, the vault beneath his bathhouse in Novigrad, and also disposes of bodies his boss wants gone, by eating them. When thieves blow a hole in the vault wall and make off with the fortune, Bart gives chase until a toxic mold gives him a headache, and he goes back to bang his head against the wall in shame. In Count Reuven’s Treasure, he tells Geralt what he saw of the break-in.

Later, in Blindingly Obvious, Philippa Eilhart escapes through the vault and puts a spell on Bart to block anyone chasing her. Geralt can talk his way past the troll by explaining he only wants to keep Philippa from harm.