Percy hadn't wanted him to spend Christmas alone at camp and invited him over. Nico had spent days trying to think of some way he could say no without hurting Percy's feelings or doing something he'd regret- after all, he was just beginning to build up his reputation after the whole Titan's thing- but with one look at Percy's stupid stupid face, he'd caved. "Sure," he could almost hear himself saying. "I'll come." And then the son of Poseidon had been so excited that Nico couldn't not show up. Also on AO3