Currently, Merlin's Mind Heart was at least half its size than before. Despite that, the Mind Heart was able to accumulate more Mind Power – at least double its volume from before.
Such a humongous Mind Power would allow Merlin's Seventh-level Mind Heart to possess Mind Powers equivalent to an ordinary Ninth-level Spell Caster.
The average Mind Power Masters already possessed extremely potent Mind Power that far surpassed the ordinary Spell Casters but Merlin's Mind Power was even greater than the powerful Mind Power Masters. Merlin had compressed the Mind Heart almost to its limit. Back then, even Wizard Ossais did not compress it to the limit.
In some sense, Merlin's embarkation was much better than Wizard Ossais, so he should be able to cultivate Nine Hit Strike more smoothly compared to Wizard Ossais.
