Fantastic Four #194
"Vengeance Is Mine!"
May 1978, in collection
Darkoth reveals his identity to the Thing, and sacrifices himself to defeat Diablo
reprinted in
*
44 Years of Fantastic Four
2005, in collection
(2005*)
*
Fantastic Four: Overthrow of Doom HB
2011, in collection
(2011*)
*
Marvel Digital Comics
no date
(no date)