The Gatherers are an army of Alexander of Brennenburg's servants who do nothing but wander the dark corridors of his castle and hunt down any unfortunate individual they happen to stumble upon.
The disgustingly deformed monsters were apparently deceased soldiers who were brought back to life via the Orb's magical necromancy powers, cursed to forever serve the Orb's current/former wielder, Alexander.. Though they are physically unattractive, they make up for their inhuman strength and speed. They are able to destroy wooden doors with an arm swipe or two and can almost outrun a fit average man such as Daniel.
Amnesia: The Dark Descent
When the young Englishman Daniel stumbled upon Brennenburg castle, he teamed up with Alexander, the baron and the Gatherers', to stop the Shadow from slaughtering innocents who get their hands on the Orb. After Daniel realizes Alexander he is a power hungry sociopath who wants to selfishly keep the Orb's power for himself, he goes on a mission to hunt the baron down. Alexander, realizing that his former ally attempting to kill him, locks himself in an isolated area of the castle and orders a few Gatherers', the grunts and brutes, to hunt Daniel and murder him.