Dr. Axel Heimskringla was Professor Sturloson's Icelandic assistant that appeared in The Grave Robbers of Genghis Khan. He was tall, and had blond hair and blue eyes. Axel was also an experienced rock climber, although not as good as John when he wished himself a better climber. He was killed in the tomb of Genghis Khan by a Mongolian death worm.

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