These are the weapons you need to beat the game. The tools of Kagrenac. Here is where to find them.

Keening- In Odrosal. Find the Ash Vampire, ask him about the Keening and Dagoth Ur's offer. It has nothing to do with the story, but its nice to know. He will attack you after awhile. Kill him for a special Amulet and a key. Use the key to open a ladder leading you to the Legendary Keening. It will be sticking in the ground.

Sunder- In Veynulal, kill the Ash Vampire for it and a special amulet.

Both these weapons require the Wraithguard in order to hold. If they are used without the Wraithguard(s), you will recieve mortal wounds of 100 HP every few seconds.