it has been mentioned on several occasions by other writers in this forum before, but I suppose it was not straightforeward for everyone:
You can speed up the game at collecting, identifying and selling items if you make best use of being bonded to the Death Knight:
You only need a merchant etc. who is living inside a house or a cave.
For example, if you collected several items and unidentifies objects during exporation of a level, and if you the have to go back a long way to the last person who is able to identify and buy them, just give everything to the death knight, until he is unable to walk! Then run with your fast and empty heroe to the door of the merchant's house, go in, and whoosh, here is your burdened Death Knight, too. This is much faster than walking with two burdened people.
Of course this also works if you have to go back from the deepest dungeon levels to the surface.
P.S. for those who say: why not take your teleporter stones? I had the located elsewhere and did not want to retrieve them just to get rid of some boring sworts and shields.