A patronus, Harry tells Neville, is the scent of freshly turned earth and the feel of the sun through the Greenhouse glass. It is working with your hands in a garden, helping fragile plants and tender seeds grow. It is being buried under friends at a Closing Feast, having won the victory through a different kind of courage. But there’s no victorious moment here, no animal appearing in swirling silver. Just a puff of smoke, insubstantial and insignificant and isn’t that just the way of it for him?
You’ll get there, Harry tells Neville. I mean, it took me ages to learn. You’ll find the right memory. Though Neville sees an uncertainty in his eyes when he says it that he’s all too used to.
And Harry is wrong. Neville doesn’t get it. Not that year, not in the year that follows, and not when Harry disappears and Neville is left to try and fill a space he knows he will never fit into. It’s his secret, the one he doesn’t tell anybody, that their leader, their hero, their general, can’t produce a patronus of his own.
A patronus, he tells so many others, is the feeling of your mother hugging you goodnight, of your father telling you he’s proud of all you’ve done. It’s family-filled Christmas mornings and sun-drenched summer days and the knowledge that you are protected, that you are safe, that you are loved. He feeds them the memories he wishes he had, and it works, for them, and he is proud of their successes. He is. He is.
And then, when the battle comes, as he always knew it would, they appear, black and lethal and full of despair. And he watches them swoop down on the battlefield, watches them prey on his friends, his soldiers, his comrades, and he fills with fury, that they dare come here, that they dare try to hurt the ones he has sworn to protect.
He is filled with fire, and he doesn’t even need the words. He points his wand, and a silvery shape explodes from its end, banishing the Dementors with its strength and size and power and fury. And as the massive lion makes its way back to where Neville stands, he knows the truth.
A patronus, he thinks, isn’t the feeling of dirt on his hands or the smell of the lilacs that grow outside his bedroom window. A patronus is a sad story told in bubble gum wrappers and vacant stares, a lifetime of criticisms and reprimands and knowing that he’ll never be good enough. It is a childhood with not enough happy memories in it, and a child who somehow overcame all that to stand where he is today.
Someday, a patronus will be the scent of flowers, the laughter of his child, the feeling of his beloved in his arms. Someday, it will be all those moments and memories he fed to others. But today, a patronus is seeing with his own two eyes that even in a world as dark and bleak and black as this one has become, there are things and people and ideas worth protecting. It is doubting yourself and your abilities and your worth, but in spite of that, never once doubting for the briefest instant that protecting those things and people and ideas matters so much more than protecting yourself.