He shows up in a bar on Kijimi, the world where Poe takes everyone to meet his Power Ranger ex-girlfriend and Babu Frik. Here's what the book has to say about him:
Rothgar is an old and experienced Corellian bounty hunter, who is likely operating under an alias. He has been subjecting himself to cybernetic replacements in a poorly planned bid to live and work forever. As age began slowing his reflexes and dulling his senses, Rothgar turned to black-market surgical clinics to replace damaged or wizened body parts with ones that will give him an advantage in his dangerous trade. Poor decision making has led to a ghastly appearance.
It also says he's wearing salvaged Imperial-era armor, repainted his favorite color. Mud brown is his favorite color? Okay then. Anyway, this is clearly a future version of Dengar, plus about 20 years of bad life choices.
Rothgar is an old and experienced Corellian bounty hunter, who is likely operating under an alias. He has been subjecting himself to cybernetic replacements in a poorly planned bid to live and work forever. As age began slowing his reflexes and dulling his senses, Rothgar turned to black-market surgical clinics to replace damaged or wizened body parts with ones that will give him an advantage in his dangerous trade. Poor decision making has led to a ghastly appearance.
