My Devourer System: Rise of the Bastard Son

There are many types of mana, but they are categorised into different types:

Elemental mana

Divine mana

Life mana 

Hunger mana

There are others, like Chaos mana, that I won't mention here, because it hasn't appeared in the story.

To use these different mana types:

You must have a Channelling technique, which is a set of instructions on how to absorb certain mana types from the air.

And a Spell, which has unnaturally shaped runes, is used to perform magic.

Channelling techniques are ranked as such:

Low:

For elemental magic, a low-rank technique can only use one element, e.g. Fire.

For Divine magic, a low-rank technique can use one spell type, e.g.Enhancement spells.

Minor:

For elemental magic, a minor-rank technique can use two elements, e.g. Fire and Water. 

For Divine magic, a minor-rank technique can use two spell types, e.g. Enhancement and Healing spells.

High:

For elemental magic, a high-rank technique can use three elements, e.g. Fire, Water and Earth.

For Divine magic, a high-rank technique can use three spell types, e.g. Enhancement, Healing and Sealing spells.

Heroic:

For elemental magic, a Heroic-rank technique can use all elements, e.g. Fire, Water, Earth and Air.

For Divine magic, a Heroic rank technique can use four spell types, e.g., Enhancement, Healing, Sealing, and Buff spells. There are two other types of Divine spells, Armaments and Defence, but I won't go into them here.

Spells are ranked similarly, based on how hard they are to master.

On the Devourer system interface, there are two stats called—Insight and Dominance.

To master a high-rank spell, you need:

[Insight: High] If your Insight is too low, you will have trouble learning the spell.

[Dominance: High]. If your Dominance is too low, you will have trouble keeping the spell in your memory.

Then, finally, we have the ranks of the magic users:

Squire: mostly use low- or minor-rank spells. When they channel enough mana for their soul to solidify, they become Knights.

Knight: There are three parts to a human: mind, body, and soul. A knight must temper all three with his mana till they break and become infused with mana. 

So Knight has three tiers—Low, Mid, and Top. Low tier has tempered one of the three parts, most likely the body. Mid has tempered two, body and mind, most times. Finally, the top tier has tempered all three, with the soul most times being the hardest.

But to become a Grand Knight, they must still glimpse their inner world.

Grand Knight: Grand Knights use Heroic rank spells and possess a powerful rune.

The others will be revealed soon. I don't want to spoil them too early. But if you have any questions, leave them in the comments, and I'll update this.