Leon's main goal was to return home; to do that, he had to do two things. The first was not to die, and the second was to obtain enough mana in order to return home using Transfer. To do both, he needed to get stronger, and the only way to get stronger was by fighting against powerful opponents. However, it was clear that the monsters of that world were way out of his league. If he fights against one or two, he might win… but not against the army of monsters that were continually leaving the dungeons.
"I need to learn and train a single spell that will stop the monsters from killing me and, at the same time, will kill them, while it conserves some of my mana."
Leon didn't know how, but it looked like the dungeons spawned between two and three monsters per minute. The easiest way to deal with them would be leveling up Fast-Conjuration until level two hundred. By doing that, Leon would be able to cast fifteen magic projectiles per second. If he could borrow Soul Eater, he would be able to do that, but Jorhorn was collecting mana to him and his friends. So, Leon's only option was to learn a new spell that was similar to Flamethrower and would be able to stop the monsters even at a low-level.
"A thunder spell will do the trick… at the very least, it will help me to keep the monsters at bay. While I paralyze them using a constant thunder spell, I will destroy their heads with some other spell that has more power. Until the thunder spell has enough power on its own."
Following the same logic of Flamethrower, Leon created a constant breeze leaving from the palm of his hand. Little by little, he increased the power of wind until it became powerful enough to become another spell.
Congratulations! You have learned the skill: Air Beam.
Cost: 40 mana per second
You obtained 01 status points.
Congratulations! The skill Air Beam has leveled up.
You obtained 01 status points.
Congratulations! The skill Air Beam has leveled up.
You obtained 01 status points.
Congratulations! The skill Air Beam has leveled up.
You obtained 01 status points.
...
"Okay… now I just have to strengthen the wind."
Leon decided to go slowly because things could get dangerous. He would have a much easier time once he obtains the powers from Volt, but things weren't that convenient. Also, little by little, the wind began to emit electricity, and since that was hard to control as always, Leon received some damage several times. Despite all that, things were going well since he was sending his concentrated mana in a single direction continuously. The number of times he got shocked were much smaller than Leon predicted. Still, since his power wasn't something to laugh at, his Thunder Resistance leveled up several times while Leon was trying to learn the spell.
Congratulations! The skill Thunder Resistance has leveled up.
You obtained 01 status points.
Congratulations! The skill Thunder Resistance has leveled up.
You obtained 01 status points.
Congratulations! The skill Thunder Resistance has leveled up.
You obtained 01 status points.
...
Leon increased his intelligence and control to learn the spell faster, but it took one week for him to receive the notification… Although his intelligence increased his powers, it looked like Leon had some affinity with other elements instead of wind.
Congratulations! You have learned the skill: Thunder Ray.
Cost: 60 mana per second
You obtained 01 status points.
"Oh well… no pain, no gain, I guess."
In the end, Leon's hard work paid off. Although Thunder Ray didn't fly in a straight line, it always hit Leon's target. Besides, the speed of the projectile wasn't something most creatures could react in time to dodge the attack. In fact, even after hundreds of years of battles, Leon doubted that even the harvesters could avoid that attack. Perhaps blocking them was possible, it would decrease the damage they would receive, but it would be painful and… shocking.
"All this trouble could be avoided if I had decided to buy potions or frequently use blue angel leaves. While I'm fine in using those to train, it isn't a good idea to rely on them in the middle of a battle. Any smart enemy will try to prevent me from using them. Besides, the moments I focus on restoring my mana will be a moment where my focus will wane."
Leon didn't waste time and went to play with the fire earthworms using his new toy. Since Leon couldn't leave the hideout to buy potions and he was still replanting his blue angel leaves, he used Mana-Eater to restore some of his mana by absorbing the energy of some trash magic items he made. He had tons of those which were made of steel, and those aren't useful anymore. So, it was time to get rid of those.
Congratulations! The skill Thunder Ray has leveled up.
You obtained 01 status points.
Congratulations! The skill Mana-Eater has leveled up.
You obtained 01 status points.
Congratulations! The skill Thunder Ray has leveled up.
You obtained 01 status points.
Congratulations! The skill Mana-Eater has leveled up.
You obtained 01 status points.
...
Although Leon leveled up that skill non-stop for three weeks, in the end, he had to use it for sixteen seconds before he could kill a fire earthworm. Leon had to use three times more mana than Magma Spear consumed. He decreased that time by half using mithril rings that increased his intelligence, but then again, Leon didn't feel satisfied with that.
"I guess I would have to keep improving while I try to stop all the monsters of a single dungeon of this world by myself…"
The time finally came to crush all the angels' camps on the continent, so Leon had to put his training on hold because that was a job they couldn't fail.