'That's one hell of a spell to get without a class,' Leo thought, watching how the fiends stumbled, unprepared to deal with a sudden slow-down of their charge.

Before he could get excited over what he could learn from just this system-based skill alone, though, Rob rushed forth.

'Good call,' Leo commented in his thoughts, watching how the older of his two younger brothers made use of the opportunity. With a sword in each of his hands, he jumped ahead and slashed with his right blade, only to use the swinging momentum at his hips to insert the tip of his sword into another monster nearby.

Then, as if all of his moves were a part of some perfectly choreographed dance, he pulled his arms back and crossed them over his chest while holding both of his swords up and pointed at the sky... Only to then slash both of them away from his chest.

The mana in the air surged towards the attack itself, filling in the space Rob's swords left and quickly building up a considerable, magical momentum.

The moment Rob fully opened his arms out, the speedy mana manifested into its physical element, creating a shockwave that threw the already stumbling fiends a few feet back.

"KILL!" The blade-wielding out of the two youths followed after Rob, exploiting the gap Leo's brother created to quickly cut the fiends along it.

Despite holding only a single sword in his right and sporting a small shield - or rather, an oversized buckler - on his left, his speed was something that sent a chill down Leo's spine.

'How can they move so quickly without any proper training?'

It didn't make the slightest sense. One's speed didn't come from just the might of one's muscles or the hastiness of one's reflexes. The human way of thinking was simply too complex to reach any level of efficiency without the extensive training required to develop muscle memory.

There was a reason why the basic knight's training regime was all about repeating the six basic swings and cuts over and over again, until the day one would get so used to them, they would still train those six moves in their damned dreams.

But here, right before Leo's eyes?

A young adult whose moves betrayed a complete lack of any sort of battle training was moving at a speed comparable to the late knight apprentices if not early and inexperienced knights themselves!

'There has to be a prize for that...' Leo thought, gritting his teeth while watching how a group of five weak humans fought off the horde.

For a moment, with Rob and the swashbuckler guy at the frontline, Mark going off to do his own share of slaughter, and Millie and the other youth supporting them from the back... For a moment, it seemed like they would have a shot.

But then, the massive number advantage of the fiends within the horde started to weigh them down, as more and more fiends simply skirted to the side, avoided the two guys at the front, and rushed straight for the vulnerable casters.

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"Mighty barrier!" the youth screamed out, sending his mana into a swirl that then half-solidified into a simple, three-layered structure.

It wasn't a proper, physical barrier that one could create by erecting a stone wall or conjuring literally any other element. It wasn't a trap kind of barrier either, with how there appeared to be no repercussions for the fiends who clashed with it.

'A half barrier?' Leo thought, when a disfigured black-cap goblin tried to smash right past the faint glow of the mana, only for it to solidify at the exact spot the fiend tried to attack.

A half barrier was by no means the strongest but by all means the most efficient kind of barrier one could erect. It didn't bear the immense cost of manifesting physical elements, lacked the burden of physically moving stuff to construct a physical barrier, and was free of the extreme burden on one's mana of pure barriers made up of nothing but magic fuel.

But there was no such thing as a free meal or an overpowered spell. And half-barrier, just like any other barrier, had a cost to it that made it as situational as any other kind of spell in existence.

'It takes one hell of a processing power and focus to keep it standing, so it would be safe to assume...' Leo thought, looking over to the mage kid and taking a short moment to stare at his intelligence-free face.

'So that's how it is.'

There was no way that youth could actually be a hidden genius capable of processing information and mana quick enough to single-handedly raise a half-barrier like that.

Still, the barrier was here. And for a few seconds, it held.

But soon, it wasn't just one disfigured black-cap trying to breach it. First, an orc joined the fray. Then, three yellow-caps started to blast it with their launchable spears. And in mere seconds, with the front of the horde stalled, the fiends spilled over to the sides, pushing tens and then hundreds of them against this single, small barrier.

'I give it ten more seconds before it fails,' Leo thought and took a shallow breath before scanning the situation once again.

The only reason why the fiends failed to cross over to the right was no one else but Mark. Apparently, he either had some insane talent or was simply an extremely adaptable person.

Wherever he went, fiends would drop dead to the ground, not a match to the powerful swings and cuts he executed without the slightest care in the world for his own safety.

Yet, as if to prove a green portal wasn't as dangerous to the system users as it would be to someone without it, not even a powerful, downward cut of an orc's axe managed to pierce Mark's skin to reach the extremely thin barrier Leo infused just below his brother's skin.

It took a damn, three-maters high troll swinging his club for Leo to sense his barrier take the very first hit... But even then, it was more about dispersing the force of the attack rather than actually blocking it.

To the front, Rob and his swashbuckler's bully were somehow keeping the fiends at bay. But to the left, where the mage erected the half-barrier...

Things were bad.

Not tragic, for the barrier still held, but just a single look at it was enough for anyone to tell it was quickly reaching its limits. It was enough for anyone to tell... fiends on its other side included.

"I've leveled up!"

The mage cried out in joy, too focused on his advancement to pay the slightest attention to the breaking barrier of his.

'Is this where I should step in?' Leo asked himself, calculating the approach, the targets, and the protection zones he would need to establish to keep his own attacks from striking those he wished to defend...

"Your barrier is breaking!" Rob shouted, somehow finding enough leeway between warding off the attacks of slightly debuffed fiends to take a sweeping look at the general situation. "Stop wasting time celebrating and fucking reinforce it!"

Contrary to Leo, Rob didn't bother holding the curses back, opting to freely use them instead, especially in a critical moment like that.

"Oh, right," the mage's enthusiasm died off when he realized just how close the fiends were to breaking through. Instead of simply sending more mana to reinforce the barrier, though...

"Mighty..."

The barrier didn't crack. The moment a single fiend managed to push his attack through it, it simply vanished, the circuit unable to cope with the number of additional calculations necessary to maintain the whole barrier with the intrusion of foreign mana of the fiend in its middle.

The fall of the barrier only served as a rallying call for the fiends who rushed ahead with renewed confidence...

"...BARRIER!"

Pac!

An already injured orc slammed into the new barrier with such force, that its body simply ruptured on the spot, splattering the whole area with disgusting, green blood.

And all of that happened a mere two steps away from the mage who now stared wide-eyed at the fiends swarming mere inches away from him.

"Okay kids, that's enough of the fun for today," Leo spoke with a sigh before taking a step forward and selectively feeding mana from the monster cores he still held in his right hand into very specific circuits of the second layer of his second legacy core.

"You can leave everything else to..."

The fabric of the space behind Leo's back started to twist and turn yet again.