The descent felt thoroughly anticlimactic. There was a central cylindrical air-filled chamber filled with stairs and viewing platforms wrapping around an elevator shaft in the middle, all surrounded by water beyond walls built using blue magic, for pressure-resistance, magic-resistance, and transparency. And that was it. That was the whole thing. A lot of that, forever.

"The place is just empty," I said.

And it was true. Whatever was at the bottom had long ago eaten everything in here. We didn't think it would make much difference if it had kept some guardian monsters around, in terms of its survival chances. We were too powerful. But, at least having something to fight on the way down would have made the descent more interesting.

"It's frustrating," Izena said. "I had fantasies of epic monsters shooting at Us through shattered walls, then I would need to shoot back quickly to kill them, with You shielding Us and repairing the walls to keep water from rushing in, while simultaneously needing to purify the mental assault. Instead, the enemy couldn't control its gluttony. This place is just a big, dumb empty vat of water with a bunch of viewing platforms and staircases from one to the next. We're literally Goddesses descending thirty leagues of stairs for the sake of world peace. I'm sure that having a bunch of open staircases with views of the aquarium the whole way used to be interesting, when there were things alive in the water, but no, the final boss gauntlet is one of boredom: How many staircases can We endure before We get bored and leave? We'll die of boredom. I want My resolve back."

I could see where She was coming from, but I didn't mind the ease of Our descent as much.

Izena punched Our palm. "Wait, little Sister, I solved the puzzle! That is its strategy! It knows it can't beat Us in a direct fight because We are so ridiculously magnificent, so instead it's hoping that We get bored halfway down and leave. It almost worked! The bastard is more clever than I gave it credit for. It almost had Me. I need to reevaluate My opinion of its intellect."

I love My Sister, cockiness and all.

Although We were complaining about the Endless Stairs of Infinite Boredom, We could have floated down the elevator shaft instead, but We had discarded that option as too risky. We would have no maneuverability, and limited awareness of what was going on outside the shaft. What if something broke the walls and water rushed in? The entire structure might implode before We knew what exactly was happening. We had to take the stairs, so We could see the water on all sides at all times, just in case.

Then about ten stories later.

"And the worst part is We're going to need to climb all of these same stupid stairs on the way back up. All thirty leagues of them. This is the worst thing that's ever happened to Me since dying."

"We could fly up the elevator shaft on the way back up. There would be no need to be cautious then," I pointed out.

Izena slapped Our forehead.

"Oh, that is a relief. Thanks," Izena sighed. "I forgot. Wow, that took a load off."

Another ten stories later.

"In a way, this whole situation is an apt demonstration of what this thing's 'ideal world' would end up looking like. It would eat everything, and be left alone in the dark, starving to death, in the most boring world imaginable," I said, to fill the time. "If it could just have controlled itself, allowed the monsters above it to live and keep breeding, it would have had a continuous supply of food, and might be strong enough to resist Us by now. But it couldn't, it didn't, and now it's too weak. It will die as a direct result of its own gluttony."

Izena nodded.

"That is a pleasant way of looking at it. I do like poetic Justice."

I rolled Our eyes. I'm so glad She's back.

Then another thirty stories later.

"If only blue mages had survived, then We could just keep the amulets charged, keep it contained, and let it starve to death as a result of its own inability not to eat everything the moment it can," Izena complained.

Even though We were complaining to pass the time, We proceeded carefully.

First and foremost, I had to maintain the purification channel. Our enemy had never stopped trying to control Us and it would grow stronger as We descended, but I wasn't strained at all yet in keeping it repelled. And, We had never stopped feeling its terror. That gave Me confidence that it wasn't trying to lull Us into a false sense of security and boredom-induced carelessness. It was genuinely trying with everything it had. But, there was an outside chance that the feeling of terror might be part of its deception. If I let My guard down, it might suddenly strike with a much stronger mental assault. Still, based on the fact that the storm fly had been able to sense that it feared Us, it seemed unlikely to be faking. It had no reason to fake being afraid of Us then, so it probably wasn't now.

Second, We still kept a constant watch on the water. The possibility that it did have guard slaves waiting to strike, but lower down, couldn't be excluded. If something broke the walls, I would need to repair them immediately. We kept a hand on the structure at all times for this reason.

We kept descending and descending and descending. The monster's red magic became stronger as We went, but I was the Goddess of Salvation, and I had purified this thing's corruption more times than I could count. It never reached a concerning level. I was always able to remove the spell faster than it could spread, and that seemed to be its only magical means of defending itself.

It was afraid of Us for good reason, as it turned out.

Finally, after more than a full day of doing nothing but climbing stairs and opening doors to new stairs, We at last reached the bottom, and saw the only living thing in the entire facility, centered beneath the floor of the cylinder.

"It's big," Izena said. "Makes sense, considering how much it ate. And, it's deep down in the ice. Oscanion was not exaggerating when he wrote that no human attack could penetrate that far."

We couldn't see the form of its actual body, since it was covered by a gigantic shell with the telltale blue appearance of something grown by blue magic. It looked like it might be vaguely spherical, so large that We couldn't estimate the size properly since it stretched off into the blackness of the abyss on all sides. It was embedded deep in the ice comprising the ocean floor.

"That's...I'm not sure what I expected, but this isn't it. It feels like the world was brought to its knees, half-exterminated, by a big dumb immobile rock whose primary defense mechanism is to mentally scream in terror at its approaching enemies," Izena said. "And its motive was that it wanted to become a bigger and dumber rock by gorging itself. There's no closure to this. It's stupid."

I mean, yes, but let's focus on the task at hand.

"I don't like the idea of not vaporizing the whole thing," I said. "We don't know enough about its nature. Leaving a little bit of it alive might allow it to regenerate."

Izena thought for a while.

"We'll only get one shot at this. Any attack powerful enough to kill that whole thing will absolutely ruin this structure. It will implode so severely that there is no way You will be able to repair it. We need to blast it to hell, get in the elevator shaft, and fly up faster than the whole place falls apart. Whatever We do, needs to be absolutely assured of leaving nothing behind, but I don't..."

She punched Our palm again and smiled ferociously.

"What, what?!" I said, breathless. "For You to be like that, this must be good! Tell Me!"

"It's all deuterium in the water and ice down here. That was in Oscanion's notes."

"Yes...?" What is She getting at?

"I can make things really hot now, like really really really hot, and the pressure out there is significant, too," She continued.

"I know, but what does that have to do with the deuterium?"

"What happens when nearly pure deuterium gets really, really, really hot, little Sister, especially under significant pressure? Didn't You have a stargazing hobby for hundreds of years?"

What does deuterium being hot have to do with...Oh.

Oh.

Like really hot. Like really, really, really hot.

"You...are You serious?!"

"A real Goddess goes astrophysical on Her enemies," Izena said, grinning.

I started giggling, doubling Us over with anticipatory glee. This was going to be a really big boom. The biggest.

"Little Sister, You have a fetish. Get help," Izena admonished when I finished.

She's not wrong, but, "You do things this way to trigger it. Don't pretend innocence."

Izena shrugged.

"I do love poetic Justice," She sighed out in satisfaction, the feeling radiating from Our chest. "Killing this thing, which lives at the bottom of the ocean in permanent darkness and attacked the surface, with the closest possible thing to bringing the Sun itself to its lair, as a Fused Goddess wearing Sun-themed regalia, with the detonation performed by the same Goddess of Justice that it tried to burn away, except She was resurrected by the Sun Goddess shining Her Light very brightly, and the fuel for the detonation was placed here originally in an attempt to use merciful means to get it to leave peacefully, which it refused...it's so perfect. I'm in awe. It's a masterpiece."

I was trembling, We were trembling, in anticipation.

"Mmmhmmm...This will be spec-tac-u-lar!" I sang gleefully.

"Excessive!" Izena replied.

"Extraordinary!" We said together, giggling like idiots.

We were still laughing, when Izena started swinging Our arms, as if limbering up for exercise.

"Little Sister, how strong did You say Your shields are now?"

I smiled nostalgically, but took the question seriously and thought for a moment. I wasn't sure exactly how big an explosion We'd get, so I couldn't do a precise calculation, but I was pretty strong now.

"The high pressure water will help to contain the explosion a bit, making it easier. Since I only need to make one shield, just for Us, it should hold," I answered. "And, We can ride the blast wave up the elevator shaft. Sadly, We will need to skip that exciting ascent that We were so looking forward to. Also, I can incorporate some black mana into the shield matrix to help absorb the radiation."

Izena heaved a content sigh. "A real Goddess does not climb stairs. She does not even use the lift. She ascends to the sky riding a blast wave."

We could still feel its blind terror, now mixed with a tinge of despair, through its desperate telepathic assault.

"Don't feel too bad about how pathetic and anticlimactic your resistance was," I said to it, unsure if it would understand. Mocking anathema while in the process of smiting it was a new tradition that must be upheld regardless. "The moment that I resurrected My Sister, your story was over; the rest was Us going through the motions. You have been condemned by a pair of immortal Sister Goddesses, Whose attacks can't be repelled and Whose defenses can't be penetrated. In the face of literal divine intervention, what other outcome can be expected? You never stood a chance, and you knew it. We are Goddesses. You cast red magic and like to slurp rotting corpses through straws."

Izena applauded.

"Savage," She giggled. "Relentless teasing, badass magic immolating villains, and My cutie pie Sister roasting idiots. The full trifecta. This turned into a really good day. What a good day to be alive again. Ready?"

"Go for it," I answered, shield already in place. "Let's go astrophysical on that thing."

Justice walked Us over to the elevator shaft, then ignited the inferno directly underneath the floor of the laboratory. The floor of the ocean began roiling, destabilizing, and suddenly exploded. A few seconds later, We shot out the top of the cylinder on the blast wave.

My shield finally shattered when We broke through the roof. I only had enough strength to make one shield strong enough to protect Us from Izena's nigh-suicidal final attack, but I didn't need to make any tough choices about Who to shield.

I healed Our blindness, deafness, and whiplash injuries as We began to fall back toward the ground.

I was weeping in joy.

"That...that was the most beautiful thing, that ever blinded Me," I gushed. "It was Your Greatest Masterpiece."

"I think it might be dead," Izena deadpanned.

"We said it would burn, and real Goddesses always keep Their promises," I replied.

We summoned a platform with the last dregs of Our mana, and flew towards the waiting Guard to convince them that their Goddesses hadn't left them, and were never going to leave.

The smoking remnants of the Southern Marine Research Laboratory were little more than black soot, smeared on the side of the cliff.