Terms: Power Level

The scale of the Leray power level was initnally designed by mages who personally tested all of the spells and their attack power by absorbing it for themselves. As technology evolved, power level for all unique spells was recorded using machinery monitoring ME dispersion rates in proportion to damage levels compared to the highest power level. The power level of any respective spell as well as their user's output level of a spell is scaled on a unit from zero to ten. The value represents how powerful the spell is; usually changing the overall result of damage on average targets, or the chance of success for spells causing status ailments. A spell with a power level of 0 does not exist, as it is simply a concept of no effect from a lack of a spell. A power level of 1 could mean none if any damage is done to a target, and is the base minimum for all low level spells. And a power level 10 is the highest power level availible in most spells.
Exceeding Power Levels: The concept of exceeding a power level ten could be possible if that spell's offensive abilities exceeds that which has been tested as the most powerful spells and reported by the Leray mages. But the scale has stopped changing since the 1950's, because after a high enough offensive level, the veil of protection becomes ineffective to block out some of the damage done by those spells. Therefore, any spell exceeding a power level ten is considered dangerous and should be used with care.
Note: The power level of spells as recorded in spell books, or pocket book of spells is based on average levels in relation to wielders. Spells used by the same wielder multiple times over a long duration of time will become more powerful, included in that upgrade as a small boost to the relative power level of that spell. Additionally, certain spells inflict small separate instances of damages through projectile barrages or over time, and exceed power levels of ten collectively despite causing no harm, and are therefore referred to as collective power levels since the term measures the factor over the entire spell's potential to reduce HP stats.