Curse of Achilles

The Curse of Achilles is a power that a person can acquire when they bathe in the River Styx.

Description
The curse is named after Achilles, the Ancient Greek hero, who was famous for his invulnerability. When one bathes in the River Styx, they will be granted the power to remain uninjured by any means. They must get their parent's blessing, however, before bathing in the river or it would kill whoever entered its' shores.

When one bathes in it, the person must envision one thing that ties them to the living. They also must imagine a single spot on their body that will be vulnerable and a rope tying them to the mortal plane. If they do not do this they will turn into ash and be forever lost in the River Styx. Though not proven, the thing a person usually envisions is often someone close. An example of this is when Percy bathes in the Styx, he envisioned Annabeth, the girl he loves.

Exposure to the water of the Tiber negates the curse permanently, because it is a Greek blessing/curse that could not be retained in territory belonging to the Romans (i.e. Camp Jupiter), the enemies of the Greeks, according to Juno.

Abilities
Anyone who bears the Curse of Achilles is nearly invulnerable, except in one weak point. They also get highly increased strength, speed, reflexes, endurance, and fighting skills. Percy was powerful enough to defeat Hades, Hyperion, a hundred skeletal warriors created by Hades, and a fraction of the Titan army equivalent to hundreds of monsters.

Weakness
The most obvious weakness is the mortal spot the person chooses, as it remains the only place that can be injured. If this spot is even slightly injured, the person will die immediately.

The less obvious weakness is a secondary function - in addition to gaining invulnerability, someone with the Curse of Achilles also gains extreme physical powers - heightened strength and reflexes - and a body that almost automatically fights. However, this places an enormous amount of stress on the body, requiring a warrior under the curse to be careful not to over-exert himself, which happens more quickly than before. Chiron said that Achilles himself took about twenty naps a day—it sometimes seemed that when Achilles wasn't fighting, he was either sleeping or eating. This means someone under the curse will tire fighting quicker than someone who isn't; meaning they could be neutralized by being put in a position where they must fight, and making sure their enemies are expendable. It is also mentioned that a person under the curse will have certain emotions or behaviors enhanced, normally having to do with their fatal flaw. One major weakness is that while you are immune to weapons you can still be killed by poisoning, burning, drowning, asphyxiation(lack of oxygen), strangling, electrocution, diseases, starvation, and frostbite.

As a Greek blessing, according to Juno, it has to be removed when entering Roman territory. This leaves the bearer of the curse vunerable to attacks.

Trivia

 * When Percy was trying to pick his Achilles' heel, he said he didn't want to pick an embarrassing spot like his armpit. Later, when Luke asks for Annabeth's knife so he can kill himself, his Achilles' heel is under his left armpit. However, Percy says this was a good idea.