Experimentation

hehe... Kai was giddy with happiness, while he'd only brought forth a small flame; he'd actually done magic! The spark, not waiting for Kai to relish in his happiness, disappeared with a final puff of smoke. 

Repeating his command in his mind, more fireballs appeared around him in an instant. It's kind of weak though. Kai thought as he saw the fireballs disappear. Let's try this. Concentrating once more, Kai chanted a made-up spell in his mind.

Oh, Fire of Provenance, gather your strength within me and provide me your power! Fire Ball

This time, a larger fireball appeared instead. It was almost thrice as large as the old one and was incomparably more stable. The smaller fireballs took merely 5 seconds to dissipate, whilst the new ones remained for 30 seconds without much change.

Kai could feel the newer fireball had taken roughly the same amount of mana, yet was much stronger than its predecessor. Kai hypothesized that it was related to his imagination, the longer chant allowed him to unconsciously imagine the image and properties of the fireball better.

Fire

Kai thought in his mind, imagining a large ball of fire appearing in front of him. A towering ball of fire appeared in front of him instantly, its flames looked unnatural and seemed to form waves on the surface, not to mention it was... black? Okay, his mind may have strayed just a little bit whilst imagining the fire.

This cluster of fire was much deadlier than both its predecessors. It instantly vaporized anything Kai threw at it, from buckets of water to chunks of a boulder he found nearby. Like, literally disintegrated. He couldn't even see the stone change into a molten state, seeming as though it sublimed.

That... is a slight improvement. Kai thought sarcastically. In all honesty, he thought it was absurd, he was sure the main reason for its strength wasn't simply because of its unique black flame, no, the main reason was the way he created it.

Kai was right in his hypothesis. Imagination was crucial in Magic, at least generating images in your head is. However, Kai had an unnaturally powerful imagination ability; courtesy of his body. So you can probably connect two and two together. 

Checking his Mana reserves, he could see they were rapidly increasing to their original amount. He'd found out that his Mana Reserves couldn't grow naturally (Well, he could although it's very, very slow and inefficient.) and that used Mana would replenish itself until it reached the limit of his Mana Reserves.

Mana Reserves, as he liked to call it, is the limit of his "Permanent" Mana that could be increased by him absorbing Mana. On the other hand, Mana is a "Temporary" Mana that can be expended but replenished over time. Just like in games. Kai mused, although, I don't think my Mana Regen is supposed to be this fast. 

Kai's Mana Regen speed was insanely fast. The amount of Mana he used to summon that deadly ball of fire was not even 1/10 of his total Mana, and even the amount expended was quickly recovered within a minute.

Kai knew this was not normal, definitely not. If all the lifeforms in this world had the Mana Regen then there's no way the world wouldn't be in ruins right now. Nonetheless, Kai was proud of the fact that his new body had so much potential.