"Whenever feasible, eat the rude," or as Lecter himself once opined, the "free-range rude." Stephen King's proclaimed "great fictional monster of our time" wasn't his creation, but Thomas Harris's.
Hannibal lives in the past, just not like the rest of us. He's the epitome of the refined monster, a psychiatrist who treats patients and opposers like meat puppets he'll eventually dine on. He's a pop culture icon known for his run as the cannibalistic serial killer The Chesapeake Ripper, but like most pop culture, we do Hannibal a disservice.
His intellect and savagery stem from tragedy. As children, he and his sister Mischa fled Lithuania trying to evade Soviet notice before being captured by a tank crew. He's made to watch the starving, dead-eyed soldiers cook and slowly eat Mischa, his sole remaining anchor to humanity.
The trauma catalyzes Lecter's two most notable characteristics. He eats those he feels transgressed by, and he remembers everything. Harris's 1st 2 books see Hannibal behind bars as a sometimes forensic consultant assisting the FBI to suss out other serial killers, but Hannibal doesn't mind, because his mind is a palace.
First popularized by Sir Arthur Conan Doyle's Sherlock Holmes' technique of the same name, Hannibal is content to live entirely in his cerebral fortress. It's become an overused trope for the eidetic memory, but its roots are real, Joshua Foer's journalistic foray Moonwalking With Einstein tells the tactics world memory champions (a title he achieves along the way) use to attain total recall.
The brain is a neural web, one in which visual cues can be tied to chunks of data. We all recall in this way, but mental athletes do so with intent and fervor. Most commonly displayed in recalling the order of 5 decks of playing cards after few moments of study, the technique is simple. Champions memorize the decks by assigning each card several specific images in a particular path up to and around a familiar house until they get to the end. There are so many reference points with each it makes recall almost laughable.
Hannibal uses this technique to remember his past, a past reminding him hunger is born from vengeance, not need.