Read more about Jiren at: Wikipedia
Official Site: Toei Animation
"Jiren (???), also referred to as "Jiren The Gray" (??????, Haiiro no Jiren), is a gray alien-styled member of the Pride Troopers who served as a major contestant in the Tournament of Power. His quiet, stoic demeanor is but a glimpse of his solitary nature; he is haunted by his past losses and desperately tries to undo it all by forging his own path of justice. While fighting for justice, he has no loyalty to anyone beyond himself, believing that trusting in others will ultimately backfire. Jiren is very proud of his strength and refuses to accept the help of his comrades even in dire moments where he is under severe pressured from his opponents." - https://en.wikipedia.org/wiki/List_of_Dragon_Ball_characters#Jiren
https://dragonball.fandom.com/wiki/Jiren
Jiren has not been a contender in any CBUB matches.