A/N: Man, it's been a long time since I posted here.

This AU was originally thought of by sabertoothwalrus on tumblr.

Random stuff that happens but isn't really talked about in this fic: Katie is 22 [EDIT: I did my math wrong]; Matt is soon to be 19, Lance, and Hunk are 18, and depending on whom you ask Shiro is either 14 or 3.5. Keith is technically 24, but due to alien biology they're actually closer to 21 in age. Allura is whatever the Altean equivalent of 19 is. Keith uses both he/him and they/them pronouns; Katie uses she/her pronouns. Katie is the Black Paladin, Shiro the Red Paladin (who flies Black), Matt is the Green Paladin (who flies Red), Hunk currently flies Green, and Lance currently flies Yellow. Project Kuron is not a thing here. Nor is the Guns of Gamara universe.

Both chapter title and fic title come from "Frequency" by Starset.

"I hope that was effective enough for them," Matt said as he slumped in his chair in front of the dinner table. They had done another Voltron event, which had been packed. Unfortunately, this had also attracted the Galra. The Robeast that they had fought had, in addition to way too much armor, a rather annoying power that the other ones had had for the past couple of weeks. It was similar to the Kromar device, in that it was able to manipulate the quintessence of the paladins. That had made the battles even more tiring than they had been, what with Katie being gone and Lotor's games of cat and mouse.

He stared at the food goo on his plate, trying not to fall asleep. He was tired, but he still had several hours of programming to do. More modification of algorithms, fine tuning to find his family and Keith. There were also the various projects he had been working on, although many of them were probably going to have to be pushed aside, other than the documentation of Lotor's tactics. Matt was just glad that, so far, they hadn't had to fight Lotor and a Robeast at the same time.

"We fought a giant monster in front of them, and didn't get too beat up in the meantime!," Lance said. "We always look great, but in that case we looked even -"

"-Meet me in the control room!" Shiro said rather suddenly, bolting from his chair.

"Wait, what? We just sat down," Hunk said. "Is this an emergency? If not, can we please wait until after dinner?"

"Black's sending me a signal," Shiro called over the shoulder. "Something along the lines of 'old paladin attack base danger'?" The other paladins stood up for their chairs and began to follow him. "That means that either Zarkon is doing something bad enough to get her attention, or Katie is…" He turned around and shrugged.

"Are you getting any coordinates? If so, I can start a wormhole," Allura said.

"Um, one tic." Shiro turned around as he bit his lip in concentration. "Okay, so Black isn't sending me the coordinates, but she's going to send them to Blue, who will send them to you."

Once suited up, Hunk pulled up the scanners. "Okay, so we don't have any new transmissions from the Blade, so either this is sudden or they haven't been able to get any leaks."

"I have the coordinates from Blue," Allura said. "We'll be wormholing to an area that is approximately half a xaral away. If it's Zarkon, I don't want to be led into a trap."

It was a quick jump, only a few doboshes, which led them to a star with four gas giants orbiting it. The second one from the star, while it didn't have any rings, did have several moons that looked to be only slightly smaller than the planet Mars. The smallest of those moons, upon closer look, had metal plating on one of its sides as if it had been built up to be a base.

"Shiro, is that moon our target?" Matt asked, barely sitting in his chair.

"So I, erm, we still don't know what the nature of this is," Shiro said as he stood up and faced the team. "Everyone, get to your lions, but be careful. And Matt, well, sort of. Part of me really gets the feeling that that's no moon." The elder Paladin groaned at the reference as he jogged to the entrance of the Red Lion's hangar.

"Are you sure?" Allura said as she pulled her hair up. "According to its chemical makeup and overall structure, it seems like a natural satellite of the planet."

"We are definitely going to make a detour to Earth after this and watch Star Wars," Lance said.

"Hunk, Allura, scan the base for architecture and biosignatures," Shiro said when they departed the Castle of the Lions. The Blue lion let out one of its sonic blasts, and the Green lion paused as its' eyes seemed to grow more of a yellow-green.

"It seems fairly simple," Allura said hurriedly. "It's pretty much uniform, in fact. Just hallways and small rooms. Anything from Black?"

"Nothing new."

"Katie? You there?" Lance asked as he opened a com to her helmet.

"Knowing the Galra, they probably wouldn't leave her with her helmet," Allura said.

"Aside from for torture purposes," Matt said. He gripped the handles like they were kitchen knives, as if he could just reach out and stab the druids like they were slabs of meat.

"I've got twenty or so lifeforms; most of them are heading towards the eastern side," Hunk said. "I think Green's scanners are broken or something, though. They're saying that there's half a Galra, one and nine twentieths of humans, and a whole lot of Alteans."

"Doesn't matter," Shiro said. "We still have to -"

"Kates, don't!" a voice called out as the Paladins heard the sound of wind. All of this was highly distorted by static.

The Black lion's incessant thoughts went silent.

A single ship streaked out from the base. It was small, and beat up looking, but it was clearly Galra.

Matt fired Red's main laser just behind the ship as a warning shot.

"Voltron, do'ya read us?" a different voice said. "If so, could'ya stop shooting at us?"

"Guys, that's Katie's comm," Lance said.

"How did you get my sister's frequency?" Matt said. While he trained Red's lasers on the ship, he didn't fire.

"I'm sorry, Matt," the first voice cut in. Their voice was somewhat familiar, and it had a slight rasp to it, as if they weren't used to talking. "The Druids took her before we could get out. She gave us her helmet so we could contact you."

Shiro licked his lips. It took a couple of tries before he could form words due to how familiar the first voice. "Do you know if there were any other prisoners left on the base?"

"They've beyond helping," the second voice said. "They've practically Robeasts themselves. In the non-thinking way, not the power way."

"We're going to escort you to the Castle of the Lions," Shiro said. "There we can get you healed. Um, how many of you are there?"

"Four," the first voice said.

Matt opened a private comm. "Guys, I know it's petty since they're prisoners, but I don't trust the first of the two that spoke. I don't like how he knew my name."

"Maybe Ka… maybe she said something about you?" Lance said.

"Hunk said there were Alteans on that ship," Allura said. "We have to go after them!"

"Not to mention that they have my sister."

"We're too late," Shiro said. "Black's gone quiet; she did so when that guy screamed out her, well, maybe it's a nickname?"

"Um, actually, guys? They're gone," Hunk cut in before Allura could go and attempt to rescue the multitude of Alteans.

"What do you mean, they're gone?" Allura asked.

"I dunno, it's like they disappeared or something? Maybe they teleported, like with a Teleduv! Either way, they're not showing up on Green's scanners."

"Let's get back to the castle and help the prisoners she freed," Shiro said, ignoring the general feeling of dissatisfaction that everyone, including himself, felt.

When the ships landed in the main hangar, Coran was already there. "I brought a stretcher, in case any of them was unable to walk. Of course, I wouldn't have minded them saying so, but I'll cut them some slack."

The first of the aliens to stumble out of the Galra pod reminded Hunk of the gray-skinned gladiator they had met back on Arus The second looked like they were the child of an Unilu and a Balmeran with some platypus thrown into the mix. The third had six eyes and was very tall, tall enough that Hunk worried that they might not fit in the healing pods. Ve helped the fourth of the prisoners walk.

The fourth prisoner was probably the half Galra that Green had picked up, with their batlike purple ears and their lilac clawed hands, one of which was pressed against their side. They had long, purple-black hair that seemed to make their already pale skin paler. Their eyes were downcast and haunted; one was entirely gold while the other had a white sclera, black pupil, and violet iris.

Shiro stepped out of his lion and found it hard to maintain a leaderly gait rather than run up and wrap his arms around them. "Keith?"