Farnham (an
NPC) is the drunkard of
Tristram, the town in the first
Diablo. You'll find him on the south side of town,
always, where he sits and wallows in misery over a
pint. His trauma is believed to have been caused by the horrors he saw in the
Labrynth, on the evil raid that was led by a now-corrupt
Lazarus.
Farnham servers no apparent purpose, other than to add color. He doesn't assign quests, sell or buy items, heal you, threaten you, or anything else. If you try to talk to Farnham,
he just kind of mumbles and usually doesn't tell you anything useful. Still, the game just wouldn't be the same without him.