@Zeroth
Now that Jason was a spirit, moving through the water was little different than moving through the air. His slime body hadn't been able to submerge, merely paddling along like a beach ball, but now he felt no resistance as he floated down into the depths. He did feel the temperature change, first a comfortable cooling, then an outright chill. And he began to feel a slight pressure on all sides--his misty form seemed to naturally take on the shape of a bubble, pushed equally from every direction. None of it impeded his movement, and he didn't feel the upward pull of a living body with air in its lungs.
The light from up above faded out after only five feet or so, but the pool was much deeper than that. Ten, fifteen, almost twenty...Soon he was in an absolute, but not quite total, darkness. It reminded him of the spirit world, the monochrome filter cast over everything. The experience was made even more eerie by all the tiny, almost mote-like gray souls he could see within the tiny fish living here. But rather than black and white, this underwater world was a deeper, richer, darker blue. The few things he could see that caught a stray, refracted beam of light every so often shone a bright aqua hue, where everything else blended into a midnight sky...
There were a few things down here, that had likely been down here for some time. A handful of scattered, glittering circles...Were they coins? Gold coins!? In another spot, buried halfway in the silt and gravel floor of the pool, a large femur bone--possibly human sized. Something, perhaps a stone blade, had once been tied to its head but now all that remained were strips of something floating like seaweed. And there were more bones scattered about as well, at least a complete skeleton's worth--a skeleblin, more accurately, as it was clear most of these bones were from a Goblin or two. They looked even older than Bonie(formerly Y'tahl)'s yellowed bones had been. Likely these creatures had either drowned, or simply been tossed into the water after their death.
There was even an old wooden chest, long rotted. The metal buckle at its front and the keyhole had long rusted away, and a large hole in its side released bubbles every so often when vibrations from up above shook the water.
And there, within a shadow of the deeps, outlined by a turquoise light all its own, glittered an ornate long sword. The first few inches of its blade sat in the sand, but none of the grit nor all this time below water seemed to have dulled or tarnished it in any fashion.
It did not react to Jason's presence. But his "soul sight" could see within it, something far more potent than the influence of the Dungeon Core...Except. All of the "souls" Jason had seen thus far took the shape of spheres. They were orbs, held within the physical body, somewhere close to the being's center almost like a spiritual heart. The "soul" he could see within the sword, however, did not take that shape. Its light suffused the entire blade's structure, a construct mimicking every physical aspect of the blade with three dimensional, yet non-physical, shape. In fact, it almost seemed as if the blade itself--the steel edge, the leather grip, the engraved hand-guard--were only a shell, fragile and delicate, infused by this soul like blood infusing the veins. The sword's spirit was deeper, denser, sadder, older, than anything Jason had thus seen.
"Ja-Soon, might not want to mess wid dis one--"
"Big BIG shiny! Use da Magick Sucky on it, quick quick!"
"You. The one who awakened the Core." Jason felt Bonie and Teef go silent within him like a child backing away from a parent entering the room with belt in hand. When the sword spoke again, it was quiet at first--before raising its "voice" at Jason. "No wonder it has been progressing so quickly. Spirit! Are you still aware? State your name! Spirit?"
If Jason still had a mouth, it'd have gone dry the moment his eyes fell upon the sword before him. It's ornate beauty; suspended in an inky void and untouched by time, was nothing short of magnificent. At this moment, he was but a gnat at the feet of a giant.... One that seemed quite angry with him.
With a deep breath, Jason answered the being before him. "My name.... Is Ja-Soon... Most call me Jason." he responded, pausing briefly as he cautiously drifted closer. "What I did, was arrogant, stupid, and rash... I saw what could be a strategic advantage, and took hold of it, not thinking of what consequences there might be. Even after I learned of it's true nature, I was blind. I thought I could control it, change it-- and give new purpose to lost souls. How wrong I was."
For a moment, Jason's eyes fell to floor of the pool, ashamed of his mistakes, yet he summoned his resolve, and locked his gaze once more on the ancient presence before him. "So, you must be Undine."
"I was an Undine, yes." the sword corrected. Jason felt the water pressure shift, as if the spirit sword narrowed its eyes at him. "And you...are many things. An Ectoslime, exceedingly rare in this environment." The water shifted, carrying Jason's immaterial form on an unseen current to slowly turn him around a full circle. "Formerly a Slime Mage, also quite rare. And before that...a Human. Not of this world." The current disappeared, as did the pressure. "And most of all, a fool. A Dungeon Core can be controlled, but not by one of your pitiable level of power. Your folly was arrogance, overestimating your abilities as a small fish in a mere pond. Then again..." The sword's tone softened, and the chill of the water became less biting. "I suppose you can not be blamed for your own ignorance. This world is nothing like your own, I am sure. You lack knowledge."
Several of the small fish seemed intrigued by the movement of the waters around Jason, though they didn't seem aware of him. They swam around him--one even passed through him--until they realized there wasn't any food stirring up the waters. The rotting wooden chest let out another handful of bubbles, and its lid shifted lightly.
"I assume you know of my presence because of the Dungeon Core's ability to recognize creatures within its range. But surely you also realize there is no way for you to wield me as you are now--and even if there were, I doubt I would find you a suitable hand. If that is your reason for coming here, leave me be. If you wish to undo your mistakes and destroy the Dungeon Core, worry not--I will do that myself, when I have recovered enough of my Mana. If your business is otherwise, Jason, state it. Otherwise, I believe it would be best for you to leave the cave quickly."
Jason carefully felt the flow of Undine's magic as the water around him surged. As the churning ebbed, the former warlord continued to inch closer, until he was an inch away from the living weapon. "I came not to wield you, but to know for certain you would not fall to the dungeon... he responded assertively as a single pseudopod reached out to touch Undine. "I think you're bluffing. Despite having a direct channel leading to the core, you haven't destroyed it yet. Yes, I'm well aware you're exponentially more powerful than this entire dungeon put together... But I have my doubts about how your mana levels are at the current moment. I assume you gain most of your Mana from water entering the pool correct? The. Core. Is. Sealing. All. The. Holes. By this time tomorrow, the 22,000 gallons of water you have now is going to be all you're going to have to combat the rest of the dungeon with. There won't be any new water. That number will continue to dwindle. With every moment the undead are regaining their abilities from past lives."
The tip of Jason's wispy tendril stopped but a hair's breadth from Undine as his tone became gravely serious, "The dungeon has you listed as a boss Undine, albeit a hidden one. I need to be certain that its influence will not overtake you, despite how powerful you are. I am simply checking, nothing more-- you have my word..."
Cautiously, he reached to touch Undine's soul, not with intent to devour, but to look within.
Jason felt the sensation of placing one's finger on the edge of a razor blade when he tried to "touch" Undine--and moments later there was a crash like a wave as an unseen force repelled him. The water churned angrily in the immediate area around the sword.
"I am not for you to know! Remove yourself from me before I destroy you!" When Jason had backed off enough the spirit within the blade seemed to calm down, but its guard was still visibly raised. "Again you overestimate yourself. Even if I were to be assimilated, what would--or could--you do about it, in your present state? My power, limited as it is, is still much greater than yours. Being under the Dungeon's control would actually make me even stronger, in a sense, and you would not be able to wrench my spirit out the way you have those Goblins. You fail to recognize your own limits, Jason."
"In any case, your fears are unfounded. Since you seem to like talking a great deal I shall do the same, and answer your concerns in order." The temperature of the water lowered somewhat more. "I haven't destroyed the Core yet because I have been planning. You will understand more of these plans momentarily. I do not draw Mana solely from the water's ambient magic, though it is my attuned element. I have different Skills that allow me to recover my magic power, one of which is to take it from things that my blade cuts. The reason I must conserve my energy is because of the condition of my being." The undine's blade glimmered as it caught a shaft of light from above. "I have far more Mana than you, or any other creature in this cave. However, a large portion of it is "locked" in the magic that bound me to this sword, and in the bond between myself and a wielder. So I only have so much to use at a given moment. Another former Human, Asteria, gave me her Mana and helped to an extent, but even without external sources I will be able to recover my power after using it."
"If the Core uses its minions to seal up the cave, this pool might dwindle--but in a sealed environment, evaporation will not dilute it so much, as even the vapors will have nowhere else to go. The reason I use the water as my home is that, due to my nature, it is easier for me to move within the water and use it in conjunction with my abilities. So far, no creatures of this cave are aquatic in nature, so there are no threats to me here. This is part of my plan. When the other former Humans began digging around the edge of the pool, I was able to widen the channel and give myself a direct path towards the Core. No doubt the Core will eventually realize that although the channel was there before your control over it was broken, that it is not a natural part of the cavern--but even if they were to fill it in, I would be able to get to the core. Using the stream would simply be more convenient."
"And to at last address your concern, the Dungeon Core is not powerful enough yet--nor will it be for some time--to attempt assimilating me. Even if it could, it would find me of limited use without a wielder--and none of its minions are anywhere close to meeting the requirements to use my power. A "Hidden Boss" is usually exactly as I just said--a creature within a dungeon too powerful for its core to control. A Dungeon Core's purpose in analyzing this creature, and providing information about it to the Dungeon Boss, is to maintain a truce of sorts with it. It might provide minions or guardians for the Hidden Boss's lair, designate certain resources to be left alone for the Hidden Boss's use, or various other things. The Dungeon Core cannot control such a creature, so it tries to keep it appeased in the hopes that, should all else fail, the Hidden Boss can at least be provoked to defend its own territory from intruders--and by extent, the Dungeon's own territory will be protected."
"Since the time that you were Dungeon Boss, however, I have taken action against the Dungeon Core directly. It likely no longer recognizes me as a Hidden Boss and instead places me at the highest priority of intruder, because it knows there is no way for its minions to overcome me in direct combat."
"Right now, the game is still somewhat dangerous--if the channel has not been sealed off by the next time my Mana is fully restored, then I will be able to swim through it and destroy the Core in my next attack. If it has been sealed, I may be set back a few days as I will have to recover my power, make an assault, and then temporarily retreat once I have used my stores, to repeat the process later. The Dungeon has far fewer resources with which to continue spawning Undead, however, and with every battle that will dwindle. It will be a battle of attrition as you feared, but one in which I will still have distinct advantage. The biggest concern will be interference from outside--and also, the actions of those like you, Human souls reborn into Monster bodies. I do not understand the nature of this Curse you all bear, and have little trust thus far towards any of you."
Finally the water had calmed completely. One of the little fish swimming around Jason had now gone to investigate the bubbles coming from the wooden chest--only for something else to suddenly dart out and snatch it up. Jason couldn't refocus his senses fast enough to see what the creature had been. Only a dark shadow that had returned within the chest as quickly as it had come out. Whatever it was, however, the sword seemed to pay it no more attention than the fish. Jason's soul sight caught a fuzzy glimpse of another gray sphere, but this one was much larger than the fish--almost as large as the Dire Rat's.
"Now, Jason. I must admit that I am none too inclined towards you. I am tempted to do what I think would be best in the long run, and sever your connection to this world. With your Mana my own would be that much more recovered, and I would have a better chance to destroy the Core." The water temperature dropped much more sharply and Jason felt pressure building around him again. "But I tell you this now, and only once more. You should leave this cave, and the Core. Only return here if you bring with you a Hero. Temper your arrogance and rein in your fantasies of power--this last I say to you, because I do not trust you. You have a darkness within you that was not put there by the Dungeon Core. If it has not been mastered, and we meet again...I do not know if I shall be able or willing to stay my blade from your throat. Go."
Perhaps Undine was right, maybe he had overstepped... But until he knew better, Jason wanted to be absolutely sure that the sword wouldn't succumb to the dungeon. "I see... Best of luck then." he responded calmly as he began his ascent, slowly climbing to the top of the pool. Jason crept from the pool just as carefully he had crept in, moving away toward the exit. Once he was sure there was no nearby patrols, he abandoned stealth altogether, racing for the exit of the cave....