The child of mana title was awarded to Orion for completing the mission titled 'Fourth Aspect'.
The objective of the quest was to gain the ability to sense and manipulate Astral energy which happened to be the fourth aspect of his mana core, but to be able to unlock the fourth aspect, Orion had to fully comprehend the complexity that came with being able to manipulate spiritual energy.
However, to do this as well, Orion had to meditate and expand his mana aspect.
The moment Orion was able to do all these, the system rewarded him with the title.
This title meant that Orion had a higher mana capacity than that of other rank ten mages.
In other words, the current amount of mana flowing within his body was high enough to overwhelm any mage in the same rank or lower than his.
The system also rewarded him with a separate skill called {Mana concealment}.