The Shambling Lunatic is the boss encountered at the entrance of the Peaceful Oaks Asylum.
The Shambling Lunatic is very much similar in design to the Boss Monster except he wears a straight jacket and a muzzle.
The Shambling Lunatic will be accompanied by pipe-wielding zombie nurses who tend to hit and bite you. There will be petroleum tanks and barrels of acid in the area you fight him. He's basically a beefed up Boss Monster with an added spore attack which will mindbork you. Keep throwing the deathly containers at him and pick up black hearts from your fallen enemies to finish the battle quick.