Balor's Magical Eye

Balor's Magical Eye is one of Merlin's magic items, which is named after the One-Eyed God, Balor, that brought forth calamity and could see through his enemies.

Background
Merlin created the Magical Eye with resemblance to Balor's ability to see through his enemies and gave it to Hawk as a gift to wear as his new tag. Balor's Magical Eye is used by Hawk to give an accurate measurement of a person's overall "power level". This measurement is further divided among the person's magical power, strength, and spirit.

Power Levels
A Power Level is a person's pure fighting prowess presented as a numerical value. A person's total power level is the sum of three different values:
 * a measure of magical power.
 * a measure of physical ability.
 * a measure of composure, determination, and perseverance.

It is to be noted however that power levels are nothing more than rough estimates of one's overall capabilities and, at best, should be used for nothing more than reference. Their values can change, mainly based on the situation at hand, compatibility between powers as well as each individual's physical and mental condition and overall skill.

Though the standard differs from kingdom to kingdom in Britannia, a power level of greater than 300 is required to become a Holy Knight of Liones.

Recorded Values
Below is a list of recorded values, given in the order of Magic-Strength-Spirit (Total Power Level),of which most presented distributions are only revealed in the official fanbooks.

Trivia

 * It is interesting to note that the symbol on Elizabeth's right eye looks similar to Balor's Magical Eye. Also, a similar symbol has been seen on Meliodas' armor (on the belt and the left knee) as a member of the sins 10 years ago.
 * Gowther has stated that he is "loaded" with it. This means that he can see the power levels of others directly, without wearing it.
 * In the manga, its arms curve to the left, while in the anime, its arms curve to the right.