"Shadows over Riva (1997) is the third part of the glorious Realms of Arkania Trilogy... Something sinister lurks in the seaside town of Riva. An evil force has subverted the city's leaders, and evil things lurk in the town's sewers. Explore the huge city, dungeons and even underwater regions in stunningly detailed 3D. Adjustable difficulty levels make the game as simple or as detailed as you like."

Key from Indie Gala's current "Steel and Giants" bundle. No thanks necessary. Good luck to all entrants!

IIRC this game runs emulated on DOSBox, too.