I cannot kill this damned lich.
He heals himself.

Where is the key for the lock in the library ?
Where is the key for the vault lock in the cellar ?
How to open the door near the cells in the cellar ?

Any help ?

you do not need to kill the lich. also, as soon you deliver the requested item to the lich, he will give you the key to open the vault ( i.e. dungeons ).

Do not kill the lich and his orchestra ! They make such a groovy hypersound.
Talk to him.
He will give you a quest (to bring him a ancient relic, the Ankh with a anholy flame.
Then you get a key for that lower area.


Library ?
If you mean the room above the labyrinth, there is a key somewere in an other cornet of the labyrinth.