Flame Knuckle is encountered during the Lost Legion's hostile takeover of the Helios space station, attempting to stop Jack and his Vault Hunters from escaping alive. At first, he is fought in a Dahl powersuit, and when his suit is destroyed he continues the battle on foot.
Flame Knuckle has an increased chance to drop the Nukem.
Killing Flame Knuckle contributes towards the No Suit for You! challenge in the Enemies challenge list.
It is impossible to "farm" Flame Knuckle during his appearance in the story, as Helios Station (where he is fought) cannot be reentered upon leaving.
However, Flame Knuckle does appear during The Holodome Onslaught DLC. He will always appear midway through Round 1 and will also appear alongside an identical clone of himself midway through the Badass Round.
During Flame Knuckle's appearance at the beginning of Borderlands: The Pre-Sequel's storyline, his powersuit always begins the battle missing half of its health, as if the suit had been damaged at some point prior to his appearance. However, during his appearances in The Holodome Onslaught, Flame Knuckle's powersuit always begins with full health.