Duke has been researching during this time; the spellcasting system is convenient and fast, yet it imposes high requirements on the caster's talent and elemental affinity.
The structure of the spellcasting system dictates that those lacking talent have almost no chance of following this path, even though mastering these spells is not particularly difficult.
The wizard's casting system is different; it has some talent requirements, but they're not as high.
Even those with lesser talent can gain casting ability through systematic learning and knowledge acquisition.
Wizards fundamentally deconstruct the entire casting process, which requires considerable effort, and the learning process takes significant time.
However, once a wizard undergoes this series of learning processes, they generally gain a profound understanding of magic and related knowledge, rather than merely using it superficially.
