I found a small group of rats on a nearby stretch, no more than a dozen, just the right number to test out.

The muck rats were especially vicious, seeming to think they had found easy prey in a lone traveler as they squealed and chattered loudly. I charged in while guarding my face, avoiding some of the rocks but mainly letting them deflect off of my shield or strike against my armor harmlessly.

The rats somewhat less confident while I closed in quickly, all while ignoring their attacks completely, cutting the first one down the middle before moving on to the next. The others seemed to realize the slings weren’t doing anything, squealing as they ran in to surround me while I moved back, cutting them down and moving in the direction of the fallen to prevent an enclosure. The rats knew they had failed, half of them dead while I was unharmed. Seeing the muck rats turn to flee I gave chase killing another two before they split off in separate directions. Six dead, and it wasn’t even that difficult. 

Fighting in a group had dulled my talents somewhat, I now realized. My speed and power greatly exceeded that of the rats, and moving around more actively in a fight was an approach that emphasized this advantage more. 

After a short break to catch my breath, I set off in the last direction I had seen one of the bigger packs. Twenty minutes of walking bringing me close enough that I could hear their grunting and high pitched squealing, even if my vision remained obscured by the increasingly tall grass that now came up to my chest. The ambient mana in the wilderness aiding its growth the further out I got. 

The rats clearly noticed me. The grass bending and snapping around me cuing me in to the fact that the pack was moving in to surround me.

I kept my shield up around my face, but was not as worried about their slings with the tall thicket of grass acting as a damper. I split off to one side, going off of experience prior experience to prevent an attack from behind. I couldn't see anything until I was right upon them, relying entirely on reaction to stab while running past. I was able to kill several like this, but this pack was at least as big as the one we had killed in the morning as a group. The rats were simply too many to prevent them from surrounding me, dealing with increasing numbers by the second despite killing one every time I took a breath. All I had to do was stab down, barely taking the time to aim as my legs were increasingly weighed down by the frenzied numbers, unable to move forward any further.  

The lanky muck rats scratched and bit, but despite the rabid ferocity they showed they were simply too short and weak to get through the leather plating my legs. The bigger threat now were the slings, as the rats in the surrounding clammered in, those at the edge of the swarm had an open shot which they took repeatedly. The rocks rung off my helmet from behind me, not hurting all that much but still managing to be terribly distracting. 

The rush of experience bathed me in light, indicating I had reached my goal but the muck rats still poured in obliviously, offering themselves up to my sword. 

"Didn't I tell you to stop leveling!?" An angry and confused voice shouted into my mind, rambling on before I quickly tuned him out.  

With the bodies stacking around me the rats were now beginning to leap and climb, desperate to get at my exposed neck and face, which soon had me doubting whether I'd accurately judged their numbers. I'd already killed two dozen, and they just kept coming. The muck rats were starting to organize lines now, throwers lining the perimeter, while bulkier rats were sent into the fray. The grass around the perimeter was now completely flattened, stamped down by the passage of dozens of rats. They hadn't managed to injure me yet, but my head and neck hurt from the constant barrage off my helmet and by now my hands felt numb. Blocking rocks constantly with my shield, and having to deal with the occasional stray that rung off my sword uncomfortably. 

Seeing how many there were this was at least a proto-colony consisting of several packs. By now the mass of rats had stopped throwing themselves so suicidely into my range, somewhat afraid now as they tried to let the rock throwers do most of the work. No longer pressed from all sides I began moving forward steadily while maintaining a guarded stance to protect my exposed face from rocks, careful as to not to trip on the pile of bodies that had sprung up around me. 

The ring of bulky muck rats tried backing up, getting only so far as the line of throwers before they were forced to respond, lashing out as a group. The others behind me took this as a signal as they begun to pour in again clawing and bashing at my legs. No matter what they did these were beings that were fundamentally incapable of getting through armor, their small and weak stature giving them pitiful leverage over the primitive tools they wielded, only the one's with slings seemed to pose me any real threat. A well placed rock to my unshielded face being my primary concern. 

I cut down the defenders before tearing into the backlines, killing the slingers who had been attacking with impunity until now. The lines were broken now, the ring collapsing as I tore through the now helpless rats, each one turning to flee as I approached, cleaving and stabbing any of the rats that weren't fast enough. 

Soon I was all alone among the clearing, the reeds cut down from the presence of our battle and the mass of bodies. Fifty, sixty... at least seventy rats by the time I finished counting. Now exhausted from the long battle, I sat down amongst the filth, no longer minding it as much now that I was covered in it. My leg aching the most out of anywhere, the bite starting to bleed again after the intense combat.

 Taking out my mirror, my face and hair were covered in blood and my armor was covered in worse, bits of gore clinging to it. I pondered my attributes longer this time, still undecided on how I should spend them and looking instead at what had happened with my classes. 

[Inventory]

It appears this is the skill that System was trying to recommend, seeing as it appeared after [adventurer] hit level 10 this was supposed to an activated skill. The pattern alternating every 10 levels according to his explanation. I mentally willed myself to use the skill, not quite knowing what to expect for my first activation-based ability. 

It was as if images were being projected into my mind, ten rooms of solid stone, each no bigger than a closet, and each appearing brightly illuminated despite the lack of light, allowing me to see the room's walls with perfect clarity. Somehow I felt like I knew what to do, laying my hand on a muck rat corpse next to me while willing it into the room my mind had just inspected. 

The corpse dissapearing instantaneously as I stayed crouched over the empty space where the body had been just moments before, in mild disbelief. 

The rat body now filling much of the first room's floor. Looking to the multitudes of bodies littering the ground, I quickly invested points in the skill, stopping after the second as I watched the number of rooms increase from ten to twenty to fourty while the rooms themselves were now larger than even my home, mentally scanning through the massive rooms almost seeming like walking great empty halls. 

Every time I placed or withdrew an item required me to have an exact mental grasp or where I wanted to put it, gauranteeing this task would be something of a headache at the higher levels and indicating to me that without sufficient acuity I should not invest further. Thinking to myself while eyeing the intelligence attribute thay would almost certainly aid in tasks like these.

Walking amongst the bodies, storing them one by one while I practiced my new skill. 

I certainly hadn't forgotten the other gain, [sword edge]. Mentally willing it to activate but seeing no effect as I frowned subtly. 

It did have the name sword in it, so perhaps the skill needed one to work. Taking out my sword from its place on my hip. 

[Sword Edge]

I activated the skill, focused on the blade trying to discern what had happened. It was faint, but there certainly had been something there. A spark of transparent ghostly blue color flashed out from the tip and extending into the air a few inches before dissapearing in a flash, gone just as fast as it had appeared. 

Looking to one of the unstored rat bodies, I steadied my sword just above the skin. A mental timer of 1 minute appearing above the skill when I tried to activate it again, somewhat irritated at the revelation. 

Waiting for the timer to finish before trying again. The blade flashed blue, but nothing else happened. Moving the blade away only to notice a blade sized wound oozing out blood where there previously had been none. 

It cut through instantly and I didn't even notice. Both alarmed and pleased at the realization as I dump my remaining skill points in without hesitation, bringing the skill up to level five. The cooldown time now being a very manageable ten seconds and the range exceeding a meter. Already an incredibly useful skill, and whose full potential excited me.  

Suddenly feeling a bit more tired despite having rested after combat. Trying it out against another body, the phantom blade materialized again but shattered to pieces midway through, shards spraying through the air and disappearing. I felt tremendously weak now, nauseous and dizzy. My head spinning as I let myself to the ground unsteadily. Having to rest for a few minutes before I could even think again.