Bem, eu passei a última hora ou duas cavando mais um pouco, e finalmente desenterrei a série que eu queria! Por alguma razão eu pensei que a série não estava completa, embora pareça agora que 13 anos depois, não há mais nada na série. Obrigado a todos que responderam.
O Cavaleiro Mago por Gene Wolfe
The Wizard Knight is a series of epistolary novels written by fantasy and science fiction author Gene Wolfe. It chronicles the journey of Able of the High Heart, an American boy transported to a magical world and supernaturally aged to adulthood. Able (which is not his real name, but rather the name given to him) becomes a knight, and because of his connection with the magical and spiritual elements of the world around him is soon also dubbed a wizard.
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The setting of the novel features elements from Norse, as well as Christian mythology and a smattering of European sources, such as Arthurian myth, and involves a seven-tiered world that is separate, but not completely detached from ours.
The kingdom that Able is taken to is called Celidon, and lies in the middle world, Mythgarthr. The world above it, Skai, is the domain of the Overcyns, who are roughly analogous to the Æsir of Norse mythology, and to whom the inhabitants of Mythgarthr properly owe fealty. Terrible giants called "The Giants of Winter and Old Night", also dwell there, and are their foes. Above Skai is Kleos, which, being far from Mythgarthr, is not much explained. Two of its inhabitants are introduced: Parka, a being much like one of the Norns, and Michael, who is much like the archangel Michael. The Overcyns of Skai owe their obedience to those who dwell in Kleos. The highest world is Elysion, and only The Most High God lives there.
Below Mythgarthr is the world Aelfrice, which is primarily peopled by small elemental beings called the Aelf. They belong to a number of clans such as the Fire Aelf and the Moss Aelf, and were themselves created by the collective creature Kulili, who lives in Aelfrice still. The Aelf properly owe their worship to the people of Mythgarthr, who they call the "old gods", but often stray in their faithfulness, sometimes even tricking humans into worshiping them. Below Aelfrice is Muspel, a world of fire and dragons. Last and lowest is Niflheim, the world of The Most Low God.
Time flows more rapidly the higher one ascends in the worlds; Able spends short times in Aelfrice and Muspel and returns to Mythgarthr to discover weeks or months have passed; similarly, he spends decades in Skai and returns to find only a week has passed below. It is implied that time stops completely in Niflheim and is infinitely fast in Elysion.