"Samaritan, 5 of 6: The Fallen"
*In the aftermath of Thanos' battle with the Beyonder, the damage to the Kyln prison shorts out a vital power link, allowing one of the Kyln's most dangerous prisoners its freedom: the fallen one, first herald to Galactus, a cosmic-powered sociopath looking to even an old score with its former master! *Source: marvel.com
Thanos came to the end of the known universe looking for something....elusive. There, he encountered a beng called The Fallen One. This insane, cosmically powered creature is intent on killing his former master-- Galactus.