Here are some facts that we know for sure:

1. Percy Jackson is named after Perseus, the Greek hero who killed Medusa.

2. Perseus is one of the only, if not THE only Greek hero to not die tragically.

3. Rick Riordan is VERY careful about how he uses names throughout the series, something he addresses from the very beginning when Percy gets to camp. Percy says Zeus’s name (or Kronos’s, can’t remember which and I’m lazy right now) and the sky rumbles, and Chiron warns Percy that names have power and to use them carefully. Later, in Tartarus (if I’m remembering correctly), Percy and Annabeth are wary of using names because of their proximity to monster respawn points.

4. The only other main character named after a Greek hero is Jason Grace.

Here are some things we can assume, based on Rick’s writing style and the details he has given us:

1. A character’s name will tell you something about them. That’s a Riordan near-guarantee.

1a. For example: Piper being a reference to the Pied Piper since she can get anyone to do anything for her, even follow her off a bridge.

1b. Or Magnus and Alex being confirmed from the beginning because Rick mentioned that he stole the name Magnus from Cassandra Clare. (She wrote The Mortal Instruments, which contains a gay couple named Magnus and Alec (Alexander).)

1c. Or Leo being named after the great inventor Leonardo daVinci (not confirmed, but they’re so similar it’s hard to believe otherwise).

1d. A castellan is the governor of a castle who enforces the law around the land. They also have military responsibility. Luke Castellan. nuff said.

2. NAMES HAVE POWER IN THIS UNIVERSE. Sally literally named Percy after a Greek hero to keep his roots close in a subtle way, but she purposefully picked a Greek hero that lives.

2a. HUGE example: Castor and Pollux. In myth, sons of Jupiter. Castor is mortal while Pollux is immortal, and Castor dies. (Slightly irrelevant but Rick loves taking notes from other authors so: In The Hunger Games, part of Katniss’s film team. Castor dies, Pollux lives.) In PJO, sons of Dionysus. Castor dies during Battle of the Labyrinth, while Pollux lives.

The one exception to this rule is Jason Grace. Or so I thought.

If you read the myth pertaining to Jason (Golden Fleece, Argo the First, Medea, etc) you find out that Jason of the Argo dies when he falls asleep on his ship underneath the rotting mast and it falls and kills him. There’s a lot of other stuff that goes down, but for the sake of being succinct, here’s a link to the myth for your perusal:

The only other SUPER MEGA IMPORTANT DETAIL from this myth: Argo Jason, by cheating on Medea, falls out of favor with Hera, while in PJO/HOO, Hera actively names Jason 2.0 and claims him as her champion. (despite him being. Y’know. The proof of her husband being a jackass to her. quality time with the stepmom right there.)

Putting this all together:

1. Sally purposefully named Percy after a Greek hero who lived, indicating fear that he would die if she chose a different name

2. Names have power and Rick puts meaning behind every single name he uses.

3. Jason dies in The Burning Maze.

The real kicker is that they both die in the same way: having lost everything, with so much still to do, dying a completely avoidable death because they weren’t paying attention to what was going on behind them. There’s differences, obviously, because Jason Grace is actually a good person, but those are inconsequential as the big picture is all the same. (We see these similarities happen A LOT with Percy, especially when he kills Medusa.)

We should have known. Rick laid out all the pieces for us from the very beginning, even (possibly) going so far as to straight up tell us that one of the seven would die (again, not confirmed, I saw it in a meme and maybe his twitter? idk im ty ty).

so:

TLDR: Rick Riordan left a gigantic trail of breadcrumbs that should have clued us all in to the fact that Jason was gonna die long before it happened.