Part of assembling a golem is assembling the raw materials. This wouldn't be too hard.
I'd imagine it would have a strong stench attack and a successful physical attack would inflict disease, poison, and drowning. Presumably it would be vulnerable to fire, with the combustion of the material causing additional damage to those nearby.
There are actual cases of people using dead bodies in siege warfare to spread plague, so this isn't totally nuts. It might be a little gross for many games, though.