"Nothing, I just worked really hard" Rezen replied casually
Others only have to consume resources and sit prettily while reading magic theories to advance in rank
As for Rezen, he has to plant his own resources. If he wants to learn magic and advance his rank, he has to offer some 'nourishment' to his farm (mana stones or corpses)
Even the combination of Spirit Plants and Mutated Plant of Gold Sage Tea also has its own limit
The first time that Rezen used them, he received enlightenment. But after that, although the tea's effects were quite good, Rezen's comprehension skills are too lacking
His subordinates received a greater 'learning boost' from the tea than himself
To put it into perspective, the tea has a multiplier effect. Rezen's subordinates let's say has 100 points of comprehension skills
With the help of the tea, that 100 points turned into 200 points
