Percy should've figured out this far into the journey that a hero will always be faced with challenges.
Now, due to his carelessness, Percy struggles against unbreakable webbing while Annabeth is unable to help due to her Arachnophobia.
Percy Jackson had grown tired of being given missions from every god and mythical being he came across during his quest. Supposedly, by completing these side-quests, Percy would be granted favors that would later help him with his ultimate goal. However, he had yet to receive any gift or wish that hasn't seemingly been useless or harmful to him.
An impatient Percy finally had enough when the god Hephaestus appeared before him one day requesting that Percy find a lost item of his. The young hero figured this would be yet another dangerous waste of time, but ultimately couldn't directly refuse to help the god. Reluctantly, Percy agreed to the quest, but secretly decided that he would finish his own mission first and go back to help Hephaestus later.
After his unwanted encounter with the god of forges, Percy and his friend, Annabeth Chase, continued on with their journey. Percy decided he wouldn't tell Annabeth about his secondary quest since he didn't want to distract Annabeth from their main goal (and because he didn't want her to lecture him about his responsibility to the gods or whatever). Instead, the two of them traveled out of the city that they were in until night came around and they needed a place to sleep.
With no buildings nearby for miles, the two of them found a field to rest in. The two heroes kicked off their shoes, positioned their backpacks like pillows, and went to sleep. Neither of them knew just what awaited for them when they awoke.
= = =
Turns out, blowing off a god to go take care of your own mortal problems is a bad idea since most gods take such offense personally. Some gods might choose to retaliate against such arrogance by turning the offending hero into some kind of plant or animal. Hephaestus, on the other hand, saw this as an opportunity to try out some new autonomous, mechanical spiders he'd invented that specialized in capturing targets.
Hephaestus programmed his spider bots to target Percy and Annabeth and sent the little machines after the pair of heroes.
It took the spiders all night to travel, but eventually the spider bots had caught up with Percy just as the sun began to rise. Annabeth had already woken up and wandered off to survey the area for monsters, leaving Percy behind to get a bit more sleep. This left the young hero defenseless as dozens of spider bots climbed onto his body and began spinning webs.
= = =
Annabeth returned from her quick patrol of the area to hear the sounds of Percy screaming. Immediately, Annabeth rushed over to the source of the sound, only to find Percy leaning against a rock, struggling against synthetic webbing that was binding his arms and legs. She also found that Percy wasn't screaming so much as he was laughing, as dozens of tiny, metal creatures were crawling over his stomach, across his arms, and around his feet.
Annabeth took a step forwards, ready to help free Percy from his bindings, only to realize what these tiny, metal creatures were. They were spiders!
Instantly, Annabeth jumped back in horror as her fear of spiders kicked in. Simply looking at anything resembling spiders was enough to throw her into a panic. Percy clearly needed help, but Annabeth was unable to approach him. In her panicked daze, Annabeth failed to notice the spiders climbing over her own feet, spreading their webs and binding her to the ground.
The two heroes wound up fully cocooned in synthetic webbing. Their bodies inside these cocoons were perpetually tormented by tiny spiders crawling across their bodies.
Percy learned a valuable lesson about his responsibilities as a hero, and Annabeth's fear of spiders doubled in intensity.
