Percival and Lamorak
Two characters on the periphery in Fall to Earth were Percy and Lamar Jones, modern analogs of Sir Percival and Sir Lamorak. Percival, in particular, was an important character in the Arthurian narrative, so I felt he needed his own space. I developed and wrote the story of these two streetwise cousins from New York. There's some reflection in Percy's struggle between family and loyalty in Apollo Burn. That's a theme of the series, moving away from the Arthurian trope of everyone apparently related to everyone else and toward stronger familial threads.
Percy's struggles are real and identifiable--as much as they can be in a person who has superhuman abilities. That his loyalties shift within Apollo Burn is, I feel, a progression of that struggle. It's natural for someone to want to belong to something. Percival has had that at various points in his life, though at the beginning of Apollo Burn, that feeling of belonging now comes with a lot of doubt, as it moves him away from other things he wants to be and belong to.
Then there's Lamar, a strong character in his own right--every bit as powerful as Percy. I preserved Lamorak's relationship to Percival, making them cousins rather than brothers (as the legend says), though they are as close as brothers could be. He doesn't have the same motivations as Percy, but he has a certain insight that Percy sometimes lacks. These two are stronger together than they are apart.