As a separate, tri-ninja'd idea...
Maybe the ghost of the warlord is a recurring mini-boss who also shows up in various sidequests instead of being the bonus boss, a d instead of the previously mentioned end...
Once Tim is defeated, the dwarves offer you entrance to the Upper Realms, where you attain fame through a series of related quests. The central settlement, a dwarven fortress combining the best and the maddest of the community, is a sort of a hub for this activity; every quest you finish ends with you bringing a trophy to the dwarven king. These trophies include magical items and an Adamantine Pick. The magical items let the dwarves explore deeper, safer. Once there are, say, 13 such items in the dwarven king's possession, they will find adamantine once a Demonsbane Amulet has been brought as well, and then mined once the Adamantine Pick is brought. Shops will start offering adamantine goods, easily the best for most items, but within a short in-game period the HFS will be released. Uriel will need to promptly head into the depths of the world and face Armok, who claims credit for everything from the civil war to Tim to the death of the warlord you killed. Then, you try to kill Armok, but can't and seal the gate of HFS with the Holy Log.
Oh, and I might be able to think of some good items to add, since I'm mostly contributing ideas. I just need to know what weapons the PCs specialize in and if you can have item-dependent skills or something.