book with three worlds

[face2098]

Hi. I'm looking for a book (I think it's a series) where the idea is it's three worlds sharing the same space and about the destroy the others. There is a human world, a goblin (or something like goblin) world, and a fairy world. I remember the most about the fairy world. The fairy princess leaves and becomes queen of the dead warrior souls. The souls were there because of their cowardice in life. I remember very little of the goblin world except the one goblin was looking for some kind of key and they were good at building war machines. Sorry it's not more to go on, but I would love it if someone knew.