This is set during Book three of Trials of Apollo, The Burning Maze.

You were on Caligula’s ship when Jason was fighting Caligula. Apollo is lying against the railing bleeding out, and Piper is being held by a henchman. Jason was just barely still fighting with arrows in almost every limb. Jason falls to his knees and you feel tears burning in your eyes. Caligula raises his spear to deliver the final blow.

What do you do, half blood?