The enhancement of power is represented by the increase in the number of Spirals. As total Magic Power increases, its utilization becomes more refined, allowing one to manage greater consumption. This leads to physical enhancement because as the total Magic Power within the body increases, it feeds back into and strengthens the physique. These are the only two aspects enhanced by the increase in power Spirals.
It might not sound that exaggerated, as these aspects can seemingly be compensated for by innate racial traits or other factors. This is also why some special Races are inherently stronger at the same Level.
To bridge the gap between different power Levels, Spells are an excellent option. While some Spells have power requirements, most do not demand significant power. Throughout the entire Second Stage, one can master most Spells; all that's needed is understanding and proficiency in their use. The combination of Spells is also extremely important.
