(My firend is working on a book, and this is her interpertation of a homonculi, this IS NOT MINE! She allowed me to USE/BORROW it, all credit goes to her!)
A homonculi is an artificial human that is made of and runs on pure hatred. They are depressed creatures, that have miserable lives -as close as they can get to it- and thrive on the suffering of other's, wether they want to or not.
They have no free will of their own, they are slaves of the humans that created them, being forced to do whatever that person wants, as if in somesort of trance.
If their master/creator die, they have free will. If they die before their master, then their creator dies within three days afterwards.
Once free a homonculi will try and go one with a normal life. Something seemingly impossible. However, there is a backfire. Apperently, whoever a homoculi falls in love with, they act as if that person is their new master. As sweet as these acts of affection the creature holds, it drives the human it's with into spiraling depression, eventually the human will be made to commit suicide to deal with the problems.
A homonculi is immortal. They can go month's without eating, they cannot feel pain, they can regenerate missing body parts, they can heal their wounds within' seconds, they can fall from great heights, and land face first, and stand right back up.
However they, like anything else, have a weakness. There are two known ways to possibly kill a homonculi. The first being impossibe. They thrive on hatred. If there were no hatred in the world, there wouldn't be a homonculi. Simple and sweet.
The other way of killing them is very difficult. Or it can be very easy. It depends on what your doing.
You must get rid of the strong point in the homonculi's body. The strong point can be anything from a heart to their spleen. If this is removed from the homonculi's body, they will still be very much alive, but visibly weakened. They will reduced to a human that is very ill. They won't die and will function properly after the organ or bone is put back in it's rightfull place.
"In whatever case, I woldn't tell you my strong-point. Not that I don't trust you, but...That could be bad..." She said.