Doctor Strange was a member of the X-Men who worked with the science and magic division whose job was to maintain the force-field that contained the section of Manhattan which was controlled by the Demon Horde and ruled by Illyana Rasputin. 
When the Darkchild used Nightcrawler as her "Bamf Dragon" she teleported to the X-Men headquarters and set about trying to destroy the shield that contained the demon hordes. Sister Grimm and the rest of the science and magic teams went to help the X-Men, leaving Beast and Doctor Strange as the sole people defending the force-field. Darkchild and the Bamf Dragon teleported straight into their room took down the shield. Doctor Strange watched in horror as the rest of the demon horde escaped. His subsequent fate is unknown.