After being housed with the other refugee aliens by the Fantastic Four, he betrayed them by communicating to the Griever at the end of all Things, that Franklin Richards no longer possessed his powers and that it was the right time to strike. Lyja discovered Gringukk's betrayal and warned the Fantastic Four who prepared a plot that temporarily blocked the Griever and captured Gringukk.
credit: marvel.fandom.com
Key Issues & Appearances
1
Significant comic book appearances featuring Gringukk