"Chaotic Dr. Fate vs. the Phantom Stranger" from Dr. Fate vol.2 #3 (DC, 1987) by J.M. DeMatteis, Keith Giffen and Dave Hunt
Volume 2? Yep, volume 1 is a reprint of First Issue Special and some Flash back-ups. In Fate's first original book, DeMatteis (who would go on to write the monthly, come back tomorrow) changed the premise, turning it into something of a Shazam story, or maybe a Firestorm one (though Kent and Inza were already merging 5 years earlier). 10-year-old Eric Strauss and his stepmother Linda merge into the Dr. Fate entity, and are monitored by Nabu in Kent Nelson's body! For readers wanting to see Kent Nelson's adventures - maybe coming off his appearances in All-Star Squadron or even Justice League - this probably seemed like a bad idea. However, perhaps the cool Keith Giffen art took the edge off, and it did spawn a monthly I really loved. More of that in 24 hours' time.