From Michael Moorcock's Dancers at the End of Time series of stories.
The Morphail Effect refers to the fact that once a time traveler goes forward in time, it is very difficult to get back to when they came from. In essence, it is the Chronoflow's resistance to paradox which prevents the return to one's time of origin. Attempts at returning results in at best a few moments back in their original time before being sent forward again; at worst instant death.
In the stories, the most notable victim of the Morphail Effect was Dafnish Armatuce, whose dedication to her society and revulsion of that of the End of Time led her to risk a return, with deadly consequences.
Interestingly, there are some individuals that don't seem to be affected by the Morphail Effect. These include various members of the Time Corps (such as Una Persson), as well as some beings native to the End of Time.
The effect is named after Brannart Morphail, a denizen of the End of Time who studies time travel and collects time machines.