Fantastic Four (1961) #325
"A Christmas Tale" is written by Steve Englehart and drawn by Rich Buckler and Romeo Tanghal. Ron Frenz and Joe Sinnott provide the cover art. Our tale begins with the Human Torch, his flame still mystically out of control and burning white hot, stranded 120 million miles from Earth by the treacherous Kang. By the sheerest stroke of luck, he's discovered by the Silver Surfer who was investigating the slowing of the orbit of Mercury (a feat Kang pulled off to thwart the occult machinations of Necrodamus). Torch tells his tale and when the Surfer hears it was his former lover Mantis Necrodamus sought to sacrifice, he races Johnny Storm back to Earth with the speed of a comet. Soon, the Surfer and Mantis are reunited and she explains that for a time after her power to move from planet to planet was taken away she lost her memory of the time they'd spent together.
Their revery is soon disrupted however by the arrival of the mysterious Cotati, an alien race of telepathic plants who wish Mantis would stop her attempts to retrieve her son from them. The son, they argue, is needed as their ambassador to the universe since only he shares their heritage and remains ambulatory (as they have given up their ability to move when they concentrated on their powers of thought). To back up their demands, the Cotati have enlisted Kang and the Priests of Pama, the martial arts masters who trained Mantis to be the Celestial Madonna. A rooftop battle ensues and the FF, Silver Surfer and Mantis triumph but not before the Cotati retreat with her son into the realm of Pure Thought. Kang also gets away, vowing to return. The Mantis decides to give up her physical being in order to pursue the Cotati, ending the former Avenger's life on Earth!