Doctor Strange Master of the Mystic Arts #1

In his castle in Europe, Baron Mordo plots to steal the secrets of his former master, The Ancient One. Sending his spirit form to Tibet, he causes Hamir to poison The Ancient One's food. From his New York City sanctum, Strange senses his master's plight, and challenges Mordo to a battle in their spirit forms. After, The Ancient One warns Strange that Mordo will be a danger to them both, as long as he lives.