Magic Initiates and Spellcasters

Magic is in the air. So, Naturally, people started to think "how do I put this inside of me?" and they did. There are two kinds of spellcasting, external and internal.
Extrenal magic doesn't require putting a high-voltage gem inside of the organism, instead casters can use exoskeletons or other tools, that can let them cast spells, without putting much pressure onto the body. (dnd classes: Bard, cleric, paladin, artificer. Viterra+: factory workers).
Internal magic is used by people, who want to take spellcasting on a whole new level. There are many methods of letting magic pulse through a humanoids body. but the most used ones are gem implants and cell mutation. (dnd classes: Wizard, Sorcerer)