“Percy, let me go" she croaked. "You can't pull me up."
His face was white with effort. She could see in his eyes that he knew it was hopeless.
"Never," he said. He looked up at Nico, fifteen feet above.
"The other side, Nico! We'll see you there. Understand?"
Nico's eyes widened. "But-"
"Lead them!" Percy shouted. "Promise me!"
"I-I will."
Below them, the voice laughed in the darkness. Sacrifices. Beautiful sacrifices to wake the goddess.
Percy tightened his grip on Annabeth's wrist. His face was gaunt, scraped and bloody, his hair dusted with cobwebs, but when he locked eyes with her, she thought he had never looked more handsome.
"We're staying together," he promised. "You're not getting away from me. Never again."
Only then did she understand what would happen. A one-way trip. A very hard fall.
"As long as we're together," she said.
She heard Nico and Hazel still screaming for help. She saw sunlight far, far above- maybe the last sunlight she would ever see.
Then Percy let go of his ledge, and together, holding hands, he and Annabeth fell into the endless darkness.”

Source: The Mark of Athena