The first three Arduin tomes are known as The Arduin Trilogy. They are, in order, The Arduin Grimoire, Welcome to Skull Tower, and The Runes Of Doom.
The Arduin Trilogy contained unique new spells and character classes, new monsters, new treasures, maps, storylines, extensive demonography, and all sorts of charts and lists which detailed the Arduin "multiverse".
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