I have been right through the severed hand and have obtained 3 pieces of the machinery. Apparently the 4th is obtained by getting seeds that are in Dorn's Deep, but how do I get to Dorn's Deep. Is there a character that tells of the location of DD so it shows on the world map? Perhaps I killed that character?!? Help.

Good lord. Whatever have you been reading to make you think this?

All four machine parts are in Severed Hand. There's one in each of the towers except the west tower, where Larrel is. And one in the main part of Severed Hand on the first level. Take the lift on level three down to level two, then take the stairs down to level one. (Don't be confused by the lift that's out of order. That's the wrong one.)

And stop reading whatever has you this confused. It's certainly not doing you any good.