Avarice
because everyone suffers from it sometimes
They're entwined under the night sky, Lily shrieks and shivers as lightning bolts strike all around them, flashing and blinding him. Peals of thunder boom overhead, and Severus grabs her head, dragging her furiously across the grounds and under the shelter of the tree, laughing slightly as a leaf falls on his head and slides down his face, tickling him. He draws her closer to him, protecting her fragile body from the pounding rain, and she looks up and smiles at him, and he cannot help himself, he presses his mouth against hers and fireworks are exploding and the thunder is deafening and she's shaking her head at him and motioning towards the castle.
He's filled with avarice, with pure, simple greed. He wants another moment like that, the passion, the love, the fleeting intimacy. He wants it, and he'll do anything to get it again.
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Because I'm finished, and incredibly sad about that.