Gaster made record time to Waterfall. Perhaps it was that the raw determination in his eyes told monsters that anyone who got in his way would be punished. Or perhaps it was the extra Magic he had consumed that gave him more speed. Either way, it was only a short time before he was at the Waterfall base.

With Undyne temporarily out of action, Commander Gerson had stepped out of retirement to lead the Pure army once more. Gaster and Gerson knew each other quite well, and the old tortoise-monster was nowhere near as intimidated by Gaster as Undyne was, so if Gaster happened to run into Gerson, he knew there was a rather high chance of his solo mission being scrubbed.

The solution was simple: don't be noticed by Gerson.

Unfortunately, that was going to be a little difficult, as Gaster wanted to grab some things from the armory, which meant walking straight through the middle of the base.

Luckily, Gaster employed the "act like you belong there, and people will think you do" trick, and made it into the armory all right. Thus, he left the armory successfully equipped with a thin layer of armor under his lab coat, and a couple of small weapons.

It was on his way out of the base, heading eastward towards Snowdin, that Gerson saw him and stopped him.

"What do you think you're doing?" That was one thing Gaster appreciated about Gerson. The old tortoise was always quite frank.

Best way to respond to that was more frankness. "Going to save my sons."

Gaster really hoped he wouldn't have to fight Gerson. Blue Magic really was draining, especially with a monster with such a heavy body and strong Soul.

Gerson squinted at him. "No yer not. You'll be killed."

"The sentiment is appreciated, but really, I am perfectly willing to lay down my life for my boys."

"... Selfish."

"... What?" Gaster was, quite honestly, taken aback.

"What yer doin'? It's selfish."

"Oh? I fail to see it that way." Gaster tapped his fingers together, internally debating how long he could waste in this conversation before he should just give up and use Blue Magic. "Please, old friend. Enlighten me."

"You're  the Royal Scientist. Over half the weapons in this army came directly from you, and more'a the integrated weapons get passed from parent to kid genetically. Now, say ya go out there, 'n' ya get yerself killed. Where do we get our weapons? We don't, and we lose the war, because we have no weapons, and our weapons inventor went an' got himself killed, tryin' to be a soldier when he wasn't one."

Gaster was silent for a moment. He steepled his fingers together, closed his eyes, and took a deep breath. Then he looked at Gerson and smiled. "You are, of course, right, Commander. Now, then, would you like to know just how much I care about that?"

For a moment, they just stared at each other.

Then Gerson let out a huff. "There's nothing I can do ta stop ya, is there?"

Gaster shook his head, smile still plastered on his face. "No, no not really."

Gerson sighed again and shook his head. "Fine. Go." He started to trundle off, gesturing slightly. "Jus' don't get yerself killed. I don't like ta lose my friends."

Gaster nodded, mostly to himself, and set off again.

~o0o~

It was a surprisingly long time before he ran into any of the Corrupt.

Gaster had made it nearly three quarters of the way through Waterfall when he heard the voices. Having lived with Sans for long enough, he immediately recognized the Corrupt dialect, and hid in some conveniently tall grass. (He still had to crouch down a bit, but compared to how tall most grass was...)

Of course, this was futile. They noticed him almost immediately, since not only could they already sense him to some degree, but they also seemed to be under the affect of whatever had been going on with Sans.

So, they lunged at him.

Gaster had not come unprepared for this.

He had made two kinds of weapons. First were the integrated weapons, such as Asgore's spear, Gerson's hammer, or his own hands and Blasters. These were once solid objects, but once they were marked with the proper Runes and linked to a monster, they become Magic summonable objects. On top of that, integrating a weapon into a monster was like altering it's Magical genetic code, and was not only quite difficult to undo, but also had a chance of being passed down to the monster's offspring through said Magic genetic code.

Secondly were the more basic ones; solid objects with Magic-channeling Runes carved at specific points along them. Anyone with Magic could use these, and they were fairly simple to make. They also used a bit less Magic. Gaster intended to rely mostly on these, as his inherent fighting ability, even with his few integrated weapons, was a bit lacking in strength.

So, it was two of these basic weapons that Gaster whipped out as the two Corrupt lunged forward. One was akin to a pistol, firing enhanced bursts of Magic. The second was a blade, Runes glowing with Gaster's purple Magic at it's base and crackling along the blade.

It was mostly because he took them by surprise by lunging straight out of the grass, towards them instead of away as they had expected, but he somehow managed to dispatch both of them. It was, however, at the cost of the blade, which was broken by a Corrupt attack.

But, with a thin layer of black dust powdering his already black lab coat, he continued.

~o0o~

The cave tunnel from Waterfall to Snowdin presented a bit of a problem.

Gaster knew from Sans' story of rescuing Papyrus that there were guards stationed at the end of the tunnel, and these guards were there specifically to prevent an attack, so he would have a hard time getting the jump on them.

In the end, after another shot of his concentrated Magic solution, he decided on a kamikaze-esque run, simply charging down the tunnel with a roar, firing down the tunnel both with attacks and the pistol.

He found that, surprisingly, he had managed to take down one of the guards. The other attacked him with a brutal fury. He took a few hits to the chest, but they were nothing; just a few HP. The second guard was slain with a couple quick shots to the face.

He continued, into Snowdin.

~o0o~

Snowdin Town was crawling with Corrupters.

Gaster crouched behind a snowbank a ways from the edge of it, as to avoid detection, watching and trying to find the best way through.

But there was no best way through. The place was completely swarmed. In fact, he didn't doubt that if he took five more steps towards the town, he would have every one of them after him.

He would rather avoid that.

So he had to find a wa-

Gaster let out a yelp as his feet were yanked out from beneath him, pulling him into the air.

For a moment, he struggled, held upside down by a thick bone around his right ankle, but as a wild laughter rippled up from somewhere beneath him, he calmed down and looked down.

There was a flower.

He had heard how the Commander of the Corrupt army was "Flowey" the flower.

And it did look strikingly similar to that flower he had used for the Determination experiments, then later replanted in Asgore's garden after the experiment had been deemed a failure...

... The flower that had mysteriously vanished.

He resolved to glare intently at the unruly plant.

After a moment, Flowey calmed down, and peered up at him. "I'll admit it, doctor. This is pretty impressive that you managed to get this far."

Gaster glared.

"I mean, you're not even a soldier!"

Gaster glared.

"But, I can't let you frolic through these fields anymore."

Gaster glared.

"You're family's already caused us enough trouble!"

Gaster glared, but there was more than a bit of pride in his eyes now.

"Lucky you, though, I can't kill you quite yet! My Corrupt lord wants a word with you."

Gaster yelped again as the vine released his foot, and he hit the ground. Slowly, he climbed to his feet, only to have a vine wrap around his neck and shoulders.

"This way." Flowey said, the vine tugging him towards Snowdin.

He had no choice but to follow.

Apparently, Flowey really did have considerable influence over the Corrupters, because, although they stopped what they were doing to watch, not a single one made any sort of move to attack.

Gaster met the eyes of every single monster in that town, and gave every single one of them his most intimidating glare.

He saw, with no small amount of satisfaction, that a few even flinched when he looked at them.

Soon, they were out of the town. Flowey led Gaster through the Snowdin woods, and into the Ruins. There were more Corrupters there, but again, none did anything.

Eventually, they came to what, when the King and Queen had lived in the Ruins, had been the castle throne room.

Gaster took in the entire room, and managed to keep his expression calm. There were several Corrupt guards standing at the edges of the room. A small, cloaked figure was perched lazily on the single throne in the room. Papyrus was in what appeared to be a dog crate beside the throne.

Papyrus looked up and gasped when he saw Gaster. "Dad!"

Gaster gave him a small smile as he was dragged forward and forced to kneel in front of the throne.

There was Papyrus! Caged and scared, but evidently unharmed. That was an entire half of the reason he was here, taken care of! Now all he had to do was get him out of the cage, and go find Sans.

"So then." A childish voice laughed, and Gaster realized it was from the person on the throne. "The infamous Dr. W. D. Gaster."

"Infamous?" He grinned. "Why, thank you."

If he looked close enough, he could just see the bottom of a face under the hood of the cloak. It was grinning. "That wasn't a compliment."

"Infamy is in the eye of the beholder. I choose to take it as a compliment."

The shrugged. "I suppose. Flowey."

Gaster felt the vine around his shoulders tremble slightly. "Yes, my lord?"

"You can let go of him."

"Are you sure-"

"Yes."

The vine slid away from Gaster's shoulders, and Flowey slipped away underground.

Gaster looked at the child on the throne and stood up. "This will be a lot easier on the both of us if you just give me my children and let us go."

They laughed, and slipped off the throne. "Getting straight to the point, are we?" Gaster saw they had a kitchen knife in one hand. One small, pale, clammy hand.

"No one has to get hurt. But I won't hesitate to kill you for my sons."

They laughed again. It was a sickening sound; no one with a voice that young-sounding should ever laugh that cruelly. "Kill me, doctor? How do you propose to do that? You are a scientist, not a soldier."

Gaster nodded. "So I've been told, multiple times. And, honestly, I agree with you. I am a scientist." He paused. "But, if you will, I have one question for you..."

"Oh?" They cocked their hooded head. "What's that?"

"... Do tell me, what exactly do you think scientists do during a war?" Gaster couldn't stop the grin that spread across his face. This was just too perfect.

The Corrupt lord hesitated.

"Don't know? Okay, I'll tell you. We scientists M A K E W E A P O N S . "

With that, he reached into his inventory, pulled out two weapons, and summoned four Blasters.

§

A/N

SO, QUESTION TIME!!

I've come up with two possible endings for this arc. One of them is shorter but more feelsy, the other longer and more epic battle-y.

... Which one do you guys want?

EDIT: General consensus says battle arc!

Anyway, thanks for reading, and I hope you enjoyed it! Remember, votes and comments are not only alway welcome, but always appreciated, too!