ToME: the Tales of Maj'Eyal

Thanks guys, that was exactly the information I needed.

Is it possible to clear the relevant dungeon without getting NPC alchemist's elixir ingredients that are only available there? For example, I think I've killed everything in the Lake of Nur and the Maze, but I'm missing the Pouch of Luminous Horror Dust. Should I go back to these areas and pick them...