Bricordia then produced a small amount of fire in her hands, "This is a first tier magic. Flame. Its used by your parents or other things for day to day needs. It can basically be used by anyone as long as they have mana. This is how our magic system works. For First Tier to Tenth Tier, we have different mana minimum thresholds and maximum thresholds. Now, I want someone to explain what these threshold means. You'll be exempt for the next test tomorrow if you answer in complete."
A student raised their hands, "..."
"Ms. Verlyn, enlighten us."
Verlyn stood up, "The least threshold for a magic spell is the cost of activating the spell but without activating all of its effects." Verlyn closed her eyes as the flow of mana around her changed. "Flame." Just as she said that, a small flame appeared in her hand, "Right now, I'm currently using about five mana just to activate this spell. But it can't be used for anything else as it doesn't burn. With just five mana, I can only manifest the image of the skill, but not the burning and heat that's around it."
"Well done Verlyn. You may sit."
"Thank you ma'am." The students' attention were suddenly brought to her.
"Alright, eyes on me." Bricordia clapped her hands and the students were suddenly sitting up straight. "What Verlyn said is true in all sorts of ways. A flame imbued with very little mana can only manifest its appearance but you can't get any benefits on it. But if you go from least threshold to the minimum threshold, you can do this."
Bricordia concentrated on her mana as the flame on her hand suddenly grew in size and it begins to emit a heat around her. "I'm currently using 20 mana just to produce this small flame. But right now, its not just its appearance, but its heat and burning will happen." She then placed her hands near on a student letting them feel the heat emanating from her flame.
"But it doesn't mean that this should be the reason why you're using this spell." Bricordia began to concentrate as the ball of flames in her hand suddenly became larger and larger. "This is the maximum output for the flame spell. It won't grow any larger, and the heat won't get any hotter. Its the perfection of a spell as you could say. So this is just the first tier. But if I put mana more and more... then it'll become,"
The heat in the classroom suddenly becomes intense as the burst of mana compressed the giant flames in her hands into a small concentrated ball of fire. "Fireball!" The audible amazement from the classroom made Bricordia blush. "Ehem." But she recovered from it instantly. "So this is what happens when you try to maximize a first tier spell. It upgrades into the next tier and so on and so forth. You can skip to a certain tier if you want as long as you have the mana for it, removing the needless mana imbuing on a certain spell."
"Ms. Bricordia, what about Unclassified Spells?" One student asked.
"Unclassified Spells are pretty difficult to rank within the tiers because they have a minimum of one mana and have no maximum threshold. Anyone can use them but that doesn't mean that everyone can utilize them. I guess an example of this would be summoning familiars. Ones that you're a contract with. Familiars are considered as a spell even though they're living beings that can think and can grow with you, but they're also based as an Unclassified Spell."