In a strange sequence of events Geralt found himself participating in the robbery of the Borsodis' Auction House in Oxenfurt. How this came about is a fascinating story – which must be left for another time. Let us here focus on a few facts: the witcher was tasked with putting together a crew of expert thieves and break-in artists. One of the candidates was a certain Casimir Bassi, a demolitions specialist who had cut his teeth in the mines of Mahakam...
The dwarf's role would be to bypass the vault doors using explosives. True, Casimir seemed an unreliable partner in crime, given his oscillations between rage and despair after learning of his wife's cuckoldry, but Geralt decided to risk it and enlist the dwarf in his crew.
Bassi's method were far from subtle, but no one can deny their effectiveness. His skillfully placed explosives blew the vault door to pieces, opening the way for the crew to grab the valuables within.
Geralt and Casimir stay with Ewald:
The dwarf walked away laden with riches and clearly no longer bothered by his wife's infidelity.
Geralt sides with Horst, Casimir stays with Ewald:
The dwarf was not given long to enjoy his newly-begotten wealth, however: when the witcher and the surviving Borsodi brother dueled, Casimir supported the losing horse – and paid for this mistake with his life.