Once, when they were children, they climbed out on Bifrost and felt the bridge burn their fingers with cold.
"That's because it's made of night," said Loki, eyes shining.
"It is not," said Thor, frowning as he sucked his fingers to make them warm. "It is made of a rainbow."
"What do you think a rainbow is?" Loki said. "It's the night sneaking up on the day. And where they meet, they make all these colors."
Thor snorted. "Night cannot sneak up on day," he said. "Why aren't your hands cold?"
Loki looked down at his fingers with mock surprise, as if they'd tricked him. "The night is getting them!" He said. "They're turning blue!"
"Are not," Thor said, laughing, but then he looked. Loki's fingers were turning blue, ice-blue, right before his eyes. Loki looked just as astonished as he was. "Loki?" he said, uncertain. "Brother? Is this a trick?" But they sat there longer and longer, and then the blue was creeping past Loki's fingers into his palm, and Thor panicked. "I will not let the night take you," he said, and heroically jammed his brother's fingers into his mouth.
At once, he realized his mistake, and he sat there feeling as foolish as he must have looked, his mouth clamped like a cow's over his brother's four blue-painted fingers, as Loki laughed and laughed.
"That will teach you what ice really is," said Loki, pulling his hand free. "It's this," he whispered, and before Thor could react, he touched his lips to Thor's, and a jolt like midnight lightning went through him. Loki's mouth was very sweet, and very cold.
Thor was bright red and angry when Loki sat back on his haunches, feeling overstuffed and overwarm, at a loss for what to do with the strange, slimy feeling curling up inside his breast. "That was not nice of you," he said at last, and then he got to his feet and walked, shaking a little, back up the bridge.
Now, Loki sleeps. Thor watches him, wondering whether even his slumber is real, wondering what else was a painted lie. Behind the silver grill of the mask--the gag--Thor can see a faint movement, of Loki's lips twitching.
He imagines taking the mask away, pulling his brother close, returning that childhood kiss.
He imagines that if he did, a riot of color would burst forth from between their lips in all the colors of the world, branching from this plane of creation to the next. A line of brightness across the sky, turning slowly, slowly, to ice.