I own nothing.
Percy had decided to become a god, so Zeus offered him a choice of what kind of god he wanted to become. The choice everybody was expecting was something sea related, perhaps the god of tsunamis, whirlpools, or something along those lines. However, Percy, in all his post-battle arrogance, decided that he should become the god of warriors.
Now Ares, being the god of war, was infuriated. And, not surprisingly, so was Athena. She was the goddess of battle after all, warriors were her most loyal servants, and she would not let this son of Poseidon intrude upon her territory. Thus formed one of the oddest alliances Olympus had ever seen, its conference only through several whispered words and a few minute hand gestures. Through that, it was agreed that Ares should be the spokesperson of the two, seeing that he had a more logical cause to object. So object he did.
"Hey!" he yelled. "He cannot be god of warriors, I am!"
Athena rolled her eyes. Could he be any more obvious? If he gets the brat to have a weakness, that would be perfect. But apparently, he has taken it into his cement-filled head to argue pointlessly. "You are the god of war, dunderhead. I know that your puny mind isn't too good with words over five letters, but you should be able to see that the word warrior isn't the same as the word war." She glared at him, willing him to understand.
Apparently he did, because he glowered at Percy a little more and finally said "Since you were mortal, you will have to have a weakness."
He said it so much like a statement, and Percy was so taken back, he actually believed him. So, while Zeus was making him a god, he focused on the small of his back and remembered the feeling of Annabeth pulling him out of the River Styx-if only just for luck-and that was that.
The few weeks after the Titan war were the best weeks of Percy's life. He had become a god, seen Annabeth and Grover; it was perfect. The dead demigods were honored at a ceremony and swiftly forgotten—who cares about tragic sacrifices when there are marshmallows to be roasted?
The few weeks after that were also pretty good; he was able to keep in touch with Annabeth via Iris Messages, even though Grover disappeared from his life.
After that though, things started to get worse. He lost touch with Annabeth, and the gods forced him to move to Olympus. He did, however, draw the line. He would be coming back to camp. The pretense was teaching, when, in reality, all he wanted to do was see his friends and relax, like he had when he was mortal. He found himself wishing that one day, he would wake up to see that he was mortal, and Camp Half-Blood was the best way to grant that wish.
So when summer started again, he was really looking forward to it. It didn't meet up with his expectations, as Grover wasn't there—something about finding demigods and making sure that they stayed alive, nothing too important-but he got to see Annabeth. The Hunters also visited—because he requested it-so he got to see Thalia.
Soon, Percy became a regular feature at camp, sitting at the third table and playing with his food. He and Annabeth even began dating, earning themselves the title of "Camp's Strangest Couple".
Seeing her daughter this blinded by love irritated Athena to no end. However, she calmed herself, remembering that no matter what Percy did, he was going to die eventually. Let him wait, she told herself. Let him think that everything is fine—and then strike when they least expect it. So Percy and Annabeth stayed happy and healthy. A few decades however, when Annabeth was in her fifties, and Percy was still as young as ever, they decided that things wouldn't work out. The parting wasn't that sad—Annabeth knew it would happen eventually, and Percy really didn't care.
Percy put all his time into hunting the rest of the Titans. He trained and went out on missions very frequently. He usually was alone on these missions, claiming that campers were a nuisance because they were always dying.
He learned how to make the most of his invincibility, and how to protect himself on his small weakness, the small of his back. He began even to enjoy himself. Things were looking up, he found a new girlfriend at camp, and even though it would end up the same way him and Annabeth did, he didn't care, because his heart wouldn't be the one that was broken.
This strange new life was shattered a century later by an arrow through the back.
Thalia lowered the bow in horror, while up on Olympus Ares smiled. A hellhound had been creeping up behind Percy and she shot at it, her arm guided by the god of war. She had pinned its head to his back with her arrow. Rushing over to his side, she said "Percy I'm so sorry. Let me get a medic." Even so, she knew that a medic could do nothing for Percy, and that was assuming that he lived long enough for her to get back with the medic.
Percy replied slowly, as if in great pain, "No don't worry about me… just tell Annabeth… That I love her."
Thalia was surprised, and also slightly suspicious. "Uh… Percy, Annabeth is dead, and has been dead for a century. Besides, you have another girlfriend."
Percy stood up, dusted himself off, and said, "Yeah, I know. Man I got you, you were all, like 'AAH Percy's dead!' And I'm like 'Ha,' Cause I was pretending to be dead. You see," he said, "My real weak spot is right here." He pointed to the small of his back. "You hit me here," he said, pointing to a spot right above the small of his back. He grinned at her—an infuriating smile of superiority, one that she had put up with only because of the friendship that they used to have.
Thalia punched him on his shoulder, muttering "Seaweed brain," at him.
Ares frowned. He had missed by an inch! Something the length of his fingernail! He couldn't let anybody see this.
"What are you doing?" asked Athena, walking into the throne room.
"Nothing involving the Poseidon brat!" he snapped, which made her walk over to where he was seated, and look over his shoulder into a glowing sphere that he had conjured.
"You have horrible aim," she said.
"You do better then," he muttered. "And I only missed by an inch."
Athena smirked, and shoved him slightly to the side, perching on the edge of his throne. She didn't do anything, which slightly surprised Ares.
"I thought that you were going to kill him," he whined.
"I'm waiting for the best possible moment," she said. "Now be quiet."
The two friends walked away from the battle snickering. A hellhound somewhere behind them growled, and then ran up and stabbed Percy through the small of his back with its long claws, faster than the human eye could see.
"HA! Take that, Poseidon brat!" Ares gloated. "I guess you were right, then," he said to Athena.
"Told you so," said Athena. "Now let's leave before Poseidon catches us." Both gods hurried out of the throne room, going in separate ways as quickly as they could, but not before smiling at each other—a fast smile that only lasted for an instant.
Percy fell to his knees, then to the ground, and didn't get up.
Thalia turned around, and said "Okay Percy, you got me once, but do you really expect me to fall for it again?" After a while, she kicked him and said "Now it's just getting old. The battle's over, you can get up now."
"No seriously you can get up now. I'm hungry."
After another few minutes it started to rain.
"Fine, suit yourself; I'm going back to camp. I guess I'll just tell Claire you didn't want to date her anymore."
She walked away, and looked back, only to see Percy still lying there. "Wait, are you really hurt?" she asked.
"Well you know what they say. The boy who cried wolf and all that, serves you right," she said, in an annoyed tone. "Really, I've been standing here for what, an, hour? All because of one practical joke? Come on Percy, you got what you deserved," she said, ranting a bit. "Well, I suppose no one really deserves death, and it's not really your fault that you died, but it's just that you were a real jerk and, wait a minute. You're dead, right?" after no response she kept talking: "And I've been talking to a dead god for a while? So you can't hear me?" she asked. "So then… I never said any of that bad stuff." She concluded.
A little bit after that she decided it was time to go home, so she Iris Messaged Chiron and with a little help, started to bring the fallen hero home.
Many thanks to my beta MidnightFlyte.