Source: Guide to Korvosa, pg(s). 62
Samp was the owner of a small shop in Korvosa which was robbed by a group of Rat's Teat Boys. Bitten during the robbery, he was transformed into a wererat. Several nights later one of the wererats returned to give him the choice between joining the Boys or death. Samp grabbed a silver candelabra in self defense and crushed the wererat's skull, but also burned his own hand terribly. Samp them disappeared into the sewers under Old Korvosa.
Samp currently lives alone in the sewers engaged in a constant battle of wits with the Rat's Teat Boys who continue to search for him. He survives by guiding strangers and visitors to the sewers and Vaults of Old Korvosa. His right hand remains disfigured and unusable and he has developed a habit of licking it when he gets nervous or while speaking to others.
On nights with a full moon, Samp retreats deep into Old Korvosa's Vaults and has even discovered a path into one of the old Thassilonian complexes. He enjoys running through the perfectly round tunnels and exactingly angled rooms far from the reach of all others, but he might lead others there if asked.