Combat between dungeons is a curious thing, as spectacular as it is rare. Dungeons do not generally spawn close enough together to touch no matter how large they grow, and even if they do they generally avoid growing towards each other. If two dungeons do touch the results are literally earth shaking; the foreign mana intruding into a dungeon disrupting its control. Monsters go berserk, traps fire spontaneously and the very structure will start to lose integrity. The victor is determined by which dungeon manages to flood the opposing core completely with its own mana, effectively taking it over. If the winner was significantly stronger than the loser, it is able to take full control of both dungeons, and what happens to its new dungeon section is completely within the victors control. Sometimes they are left unchanged, other times the monster makeup is changed completely overnight. If the dungeons were more evenly matched then the winner is unable to take control of the losers dungeon and the losing core instead disintegrates, resulting in the withering of its dungeon.

- A treatise on dungeon combat

Tens of thousands of mana pathways ran through Erryn's core in complex patterns, even the widest only hair width. Erryn ran mana through each of them, just a little more than they naturally allowed. Enough to cause some strain, but not enough to risk fracture. Each time the excess bled out, Erryn repeated. Tens of times, hundreds of times, and each time Erryn could push just a little further than the last. There were stores among the pathways, containers of mana that Erryn overfilled slightly then drained, each time inserting slightly more. The pathways and stores alike grew tougher, able to contain denser mana without stress. Eventually the core could contain more than a hundred units of mana without difficulty, which was enough to spur the System into action.

Dungeon core upgraded. Maximum mana capacity increases to 100. Mana regeneration increases to 0.003/second.

But Erryn saw no reason to stop yet. The core could still take more and while regeneration had become unimportant, maximum mana capacity had been a limit too often. So it continued, cycling mana over and over, training the core to cope with more.

Dungeon core upgraded. Maximum mana capacity increases to 200. Mana regeneration increases to 0.006/second.

Now things started to get harder. Each cycle was adding less to the capabilities of the core. At the point the core could hold little more than 250 units of mana, far from the 500 Erryn assumed would be required for the System to kick in next, it stopped completely. But still, Erryn had quadrupled its System managed mana capacity. Mythril nuggets could be summoned at last, at a cost of a hundred mana.

Watching it form, Erryn realized that mythril nuggets were nothing like the other precious metals. The high mana cost was unsurprising; mana was a vital part of its structure. Rather than a material in its own right, it was more of an alloy of silver and mana. Still Erryn practised a manual summoning, thinking this a useful stepping stone to even more complex structures. And indeed, once Erryn had the hang of mythril the experience paved the path towards summoning more with the silver part of the alloy replaced with gold.

New material unlocked: Mythril
New material unlocked: Orichalcum

Orichalcum nuggets were still too expensive for Erryn to summon them via the system. Thus for the first time Erryn had created something not by copying the system but by applying its own knowledge. It may have been a simple modification of mythril, but it was still a milestone of which Erryn was proud. Although even if Erryn considered these mythril and orichalcum materials expensive, it was still nothing compared to monster costs. Given the rate of increase per rank of monster so far, and assuming the same thing held indefinitely, Erryn's current 200 mana would be insufficient to summon anything for floors beyond seven. Either Erryn was far behind where it should be on core upgrades or it was missing something with monster costs. Given Erryn's untraditional method of summoning higher rank monsters, both options were plausible.

Between the core reinforcement and summoning practise, Erryn killed enough time that the lake had come into view. White banks of salt covered the bulk of the area the lake should have occupied according to the maps, but there was still water remaining in the deeper stretches. The greatly lowered water level confirmed that this area hadn't had much in the way of rain for a long time, but beyond that Erryn knew little about weather and water cycles. Its interest in the lake stemmed from something different.

New material unlocked: Water

Erryn immediately set up fields on the surface, and at several levels inside the dungeon. Watering them properly, constructing roofs of glowing materials to provide light and planting seeds of food crops. Crops planted inside the dungeon sprouted immediately, grew rapidly, and stopped at their full size. Just like the dungeon vines they were obviously being manipulated by the System. The plants on the outside showed no immediate reaction. Time would tell whether they would grow normally or not at all. Deep in the dungeon the crops showed visual changes that made it obvious that they were affected by the ambient mana, but nothing new was unlocked. Analysis described them as mana-touched, but still the same species. While there wasn't any use for the crops right now, Erryn had secured a food supply for any future animal life, and assuming that the surface plants sprouted, the first method of restoring some greenery to the surface. Although the need for water and more light still made that use less than ideal.

The next feature to come into range was another town, Turju, surrounded by thin stone walls. It had a barrier that was still operational, but it was weaker than that of Berju and Erryn had grown stronger. Erryn ignored the resistance as it pushed its mana into the walls, simply overwhelming it with raw ability. The inside of the town was in much the same condition as Berju. It had obviously been spared from the destruction of war only to be wiped out by the final weapon. Erryn laid the remains to rest in its graveyard as it ate into the town. It found little new in the way of resources; a potion shop had a few varieties of resistance potions it hadn't yet claimed, a smithy had a couple of exotic weapons. Perhaps they were specialised tools for monsters in a nearby dungeon, or maybe Berju had simply been out of stock.

Given Erryn's new access to mythril and orichalcum materials, and what it thought about their abilities to store mana, Erryn paid special attention to the towns enchanters. Like Berju they contained reagents, but actual enchanted goods were nowhere to be seen. They had probably been requisitioned for the war effort. Erryn stored up any reagents still in good condition regardless; it was certain there would come a time when they would be of use.

As a medium sized town there were no noble residences here beyond the central manor, but Erryn still hoped for some more eccentricity from the richer inhabitants. The higher-end homes in Berju had nothing like the excess seen in stories, as much likely due to wartime austerity than social status or the exaggerations of story telling, but the one well preserved library gave hope for a similar find here. However, the only find was one home which contained a single dagger constructed of mythril, mounted on a wall. Possibly a family heirloom. More importantly, the dagger had lines of runes engraved on the blade, Erryn could see the mana within the dagger, not just saturated amorphously, but highly structured and containing several affinities. This was Erryn's next example of an enchanted item after containers enchanted with a preservation effect. Erryn stored it away, intending to investigate it thoroughly, as absorption was unlikely to grant anything on its own.

The central manor was larger than that of Berju, and considerably more ostentatious. More of a castle than a manor, surrounded by a wall instead of a fence, with unnecessary buttresses, multiple towers and spires, and gargoyles and statues lining each ledge. Parts of the roof had collapsed in, but the building was otherwise in good repair, the lack of real weather making the loss of the roof less devastating than it would otherwise have been. The insides were in poorer condition, internal furnishing generally being made from materials less hardy than brick and slate, but even the remains showed the considerable grandeur of this place. At least in comparison with anywhere Erryn had yet seen, which was admittedly not a great variety.

Erryn located preserved documents in an office, not kept with magic but simply high quality paper and ink, securely stored in an airtight safe. These primarily dealt with local concerns, and Erryn had no interest in topics such as how much tax each village had paid. There were records of the headcount conscripted for the army, but no high level information about the war that Erryn did not already know. There was some more personal writing, a diary in which the author had written personal thoughts about day to day events, and Erryn was happy to see that their opinions on the hex bomb largely coincided with its own.

Down in the basement was another core room. Although the barrier could be broken directly this time, Erryn didn't know what the effects would be of trying to interact with the active enchantments, so repeated the previous strategy of starving them out. Although this time Erryn did at least pay careful attention to the layout of the runes and the mana flows before starting, making recordings of them back in the dungeon.

Unnamed goblinoid dungeon (Withered) defeated. 0 floors captured. Foreign core captured intact. Core level too low to reinforce existing core. Adding subsidiary core.

Erryn suddenly felt nauseous, which was impressive for something with no stomach. Its vision blurred, everything doubled as if it were viewing from two slightly different vantage points. Its own thoughts echoed, making it difficult to even think. But Erryn could tell that the situation wasn't dangerous, simply different. So it took its time to get use to suddenly having an additional core, effectively giving it two brains. It could just relocate the new core into its core room, cutting the distance between them to nothing, but that would be too much of a waste. Having additional cores held at a distance to its original would permit it to reach out further into the world. But this new core was weak and slow. It needed to be reinforced and bathed in mana. For now, Erryn left it untouched, sending it to sleep, but once it again reached the limits of its expansion it would construct a new dungeon at that border.

If every town and city held a dungeon core like this, Erryn saw no reason why it couldn't expand indefinitely, even without further mana control upgrades. In fact, by the time Erryn had got to grips with its new core, its territory was approaching the area of its first city. From the maps, this cities name was Wyndblake, and was far larger than Berju or Turju. But despite the proximity, Erryn was unable to make out its walls or see any sort of structure. Perhaps the map was slightly inaccurate. It didn't matter; Erryn was taking over everything anyway, so it would find it soon enough.

The map was not inaccurate. Erryn stared into the massive crater that encompassed the entire city. It was obvious why it couldn't be seen from a distance on these flat plains; not one brick remained on top of another. Not one brick remained. There was simply nothing here that served as evidence that a single person once lived here, never mind a bustling city. Erryn needed no evidence to know full well what had done this, but the evidence was there nonetheless. In the centre of the crater, a blood red mass of pain and anger, its silent screaming piercing deep into Erryn's mind. Erryn's class writhed in indignation, spurring Erryn to do something, anything, about it. Erryn obliged.