Fodus, from Ultima VII
When the Avatar met him, he was in the late stages of a really bad silver serpent venom addiction, with his skin starting to rot and fall off. Fodus was given the venom by Mikos, the master of the mine, and forced to work even when everyone else couldn't because of broken machines. Fodus' speech started to fail from time to time, and his mind was badly damaged.
However, he did reveal that they were searching for a new substance in the mine, blackrock.