I will update the content here as the story progresses (not just add), as I don't want spoil anything.

This book divides power into two categories (Rank/Stars and Class) that work together to determine a being's strength.

Class

They are broken into nine stages based on the colour of the mana core. Below are the classes from weakest to strongest. Humans all have Black-coloured mana cores, making them of the Imp class

The stronger the core, the higher it's absolute mana storage limit, by a factor of the stage of the core's class (Eg. a violet-coloured core has twice the absolute limit of a black-coloured one).

Black-coloured orb = 'Imp'.

Violet-coloured orb = 'Goblin.' (2x Imp)

Indigo-coloured orb = 'Ogre.' (3x Imp)

Blue-coloured orb = 'Giant'. (4x Imp)

Green-coloured orb = 'Titan.' (5x Imp)

Yellow-coloured orb = 'Goliath.' (6x Imp)

Orange-coloured orb = 'Colossus.' (7x Imp)

Red-coloured orb = 'Behemoth.' (8x Imp)

White-coloured orb = 'Leviathan.' (9x Imp)

Basically, it is black + colours of the rainbow + white.

Rank

No one knows how high ranks go, but as of now, there are three known ranks. The star equivalent is for humans, while the rank equivalent is for non-human species. A mana core possesses shining white stars in humans, while a non-human possesses dark orbs instead.

Rank 1 = 1-Star

Rank 2 = 2-Star

Rank 3 = 3-Star

Filling a Mana Core

Increasing rank and class will also increase the absolute limit for a being's mana capacity. However, improving their current maximum mana storage to reach this 'absolute limit' requires absorbing mana from outside sources.

For example, someone with an absolute limit of 100 can currently only store a maximum of 10, but if they consume enough mana cores from dead creatures, they can slowly increase their maximum mana capacity to 100. However, if they try to consume more cores after this, they won't be able to retain the newly consumed mana and end up wasting a full core's worth of mana.

Mana cores also recharge naturally by absorbing mana from the environment. They do this up to their current maximum capacity, so people don't need to constantly consume mana cores to recharge their depleted mana core.

Monsters

Monsters belong in two distinct categories based on their origin, and the main way to tell them apart is by their blood. Magical Creatures had a multitude of blood colours, while Unknowns possess ash-grey liquid instead.

Magical Creatures were species that existed in the world from the beginning.

Unknowns were beings that didn't exist in the world to begin with.

They don't possess Mana arts but have racial abilities that utilize Mana.

The amount and type of racial abilities depends on the race and strength of the monster.

Artifacts

They are created from the Mana Core and remains of killed monsters, and share their Rank and Class with the core used to create them. Artifacts are able to copy some of the racial abilities that belonged to the monster who's core was used to create it.

Core Spirit

Consuming the Mana Cores of Monsters allows for a human to gain a racial ability that originally belonged to core's owner. They function like Artifacts, but instead are a direct part of the wielder's body. However this is really rare, and normally requires consuming countless cores to acquire even one.

Humans can only possess one Core Spirit at a time, and if they gain a second one, they must remove one of them.