If you create a backstory for this character, which direction would you go? Would he be a villain or a hero? A main character or minor one? Would the setting be part of the backstory?
I think settings are the most underused technique writers have. So I would use the setting to help build my backstory. Maybe he’s standing in a long-lost library, a trove of information, and then loses access to it. How would that affect him? Or this library is in his home. He acquired all these wise books and wants to pass on the information but the younger generations aren’t interested. That would definitely build a backstory for him. Or maybe he’s the antagonist. The protagonist and his buddies want in the library, and the old man prevents them. His backstory would have to explain why.
What backstory would you create for this character?