I had an idea that poped into my when while roaming the net, an i figured i'd post it here to get some thoughts on it. Anyhow here goes, oh.. did i mention i am a fan of Lord Soth?
This would be a Baldurs Gate 2 mod, you would have to play as a Paladin for X amount of levels (we'll say 12th level for now) then fall. Then at some point after having fallen you die in game and a evil deitie (maybe Mask? or Cyric?) appear and offer you immortality at the cost of your soul. Of course your gonna say yes then be transformed into a Death Knight (following 2nd Edition rules). I thought it would be a neat idea. Now of course you wouldn't get all the abilities at once they would have to be spread over X- Amount of time but over all it would be one hell of a fun kit to play.