Explanation of the Charming
You can charm on several occasion. Like when you get the merchant trying to sell you a wizard robe for 30000 gold you can attempt to charm him instead for a mana cost.
There are a few other event similar to this like the water-making pebble merchant or a possible researcher/apprentice.
It’s not a school or element. It’s a choice.
Note: Generally charming is related to Illusion. If the option doesn’t appear but you’ve seen it before, you need to level up Illusion more.