The friendly battle between father and son starts off easily enough. They both throw out a few attacks- bone shaped, unsurprisingly- that are easily avoided on either side. As the low-tension opener attacks are traded, there's a bit of conversation between the combatants.

"So, are there any particular rules I ought to know about in terms of this combat engagement?"

"well, for starters, you're not allowed to do any... weird voidy stuff."

"Weird Voidy stuff. Please clarify."

"none of that black oozy stuff."

"Sans, literally my entire body is made of this stuff."

"but no using it like an attack."

Gaster heaves an irritated sigh. "Fine. No wierd Voidy stuff. Anything else?"

"shortcuts, but no teleportation."

"Next thing you know, you'll be telling me I'm not allowed to think or move!"

"dad-"

"Can you two quit yapping?!" Undyne interjects. "I wanna see some fighting!"

"fine." Sans huffs, then meets Gaster's eyes. "ready?"

"Ready." Gaster confirms with a nod.

And it's like you blink, and the both of them are gone. Half a second and another blink later, they've met in the middle of the field and are locked in combat, bone-attacks doubling as swords. They're going all out at each other, swinging with wild yet precise abandon, amid a chaotic storm of building Magic tension. They duck and dodge and block and attack and counterattack and dance, both moving faster than you knew they could.

Suddenly, two massive Blasters appear, one Sans' and one Gaster's, high above the pair, angled downward towards the tight struggle. The Blasters fire at the exact same moment, the brilliant beams of light colliding with the ground in the same instant. You shut your eyes against the light, but you can still see it glowing against your eyelids, and the heat from the beams is still pretty hot, the roar deafening.

When you open your eyes, there's still an afterimage burned into your retina. By the time it clears, Sans and Gaster are standing again at opposite ends of the field, crouched in ready positions. There's a big charred circle in the grass, maybe nine or ten feet across, where the Blaster beams hit.

For a moment, they each stand to their opposite sides of the field, and you can see something burning bright in their eyes.

Determination.

And then, Sans and Gaster both lunge across the field again, weapons in hand, more bones and Blasters (albeit none so large as the first few) appearing in the air to attack each other. Most attacks are dodged, though a few are landed on either side, and you realize Sans' HP must have gone up by a lot, or else the attacks are non-damaging, because the few times he gets hit, he shakes it off like it was nothing.

When the pair of them meet, the concussive blast of their combined Magic impact is enough to shake the ground. And then they're dancing again, but this time attacks fill the air, each trying to gain the upper hand on his opponent through any means possible.

And then, "any means possible" becomes Blue Magic. Gaster goes flying backwards, Soul outlined Blue against his chest as Sans slams out his left hand, his left eye glowing bright cyan with intermittent yellow sparks.

Gaster hits the ground and skids a few feet, then promptly rolls to the side as several bones spear up from the ground where he just was. Sans allows the taller skeleton a moment to climb to his feet, but you see Gaster's shoulders are slumped, and there's still a blue glow against his chest. He's still under the effect of Blue Magic.

He just laughs, though, and you hear him shout something to the effect of, "glad to see that was a good investment after all!" to Sans.

Then he's running again, lunging and jumping and ducking and rolling as he charges towards Sans, avoiding every attack Sans throws at him. When he reaches Sans, he doesn't attack directly, but instead twitches his hand upward. The blue light at his chest fades, and suddenly Sans is skyrocketing, his own Soul glowing Blue.

There's a moment where Sans is high in the sky, silhouetted against the sun, his left hand raised. And you see upwards of twenty Blasters forming all around him, all pointed straight down. And then they're firing off, like lightning bolts striking the earth, and Gaster is frantically dodging on the ground below as Blaster after Blaster nails the grass around him. When the attack stops and the Blasters fade, Gaster releases his Blue Magic on Sans, who immediately takes a shortcut to the ground, rather than plummeting some forty odd feet.

Gaster summons his own mass of Blasters, now, the massive skulls with significant more draconian appearance than Sans' Blasters appearing at strange locations around the field. You barely have time to look at the positioning before the first one is firing off at Sans, who promptly takes a shortcut. Another Blaster rotates slightly before firing- right as Sans leaves his shortcut, directly into it's path.

Sans lets out a shocked cry before taking another shortcut, only to land in another Blaster's path. Sans proceeds to leap all across the field, only narrowly avoiding each Blaster's beam, until the last Blaster slams solidly into his chest, sending him flying. He hits the ground and is still.

Gaster lets out a shout, seemingly only just suddenly realizing how ferocious they had been getting, and is immediately at Sans' side. You can hear him asking Sans if he's alright, and Sans' muttered reply, at which Gaster bursts out laughing. So, presumably, Sans is okay.

Gaster offers Sans a hand up, then just goes ahead and picks Sans up, and begins carrying him back across the thoroughly-scorched field to where the group of you are standing, open mouthed.

You can hear them talking as they near.

"-ow did you do that?" Sans is saying. "knowing where i was gonna land?"

"For as much as you're aware of space," Gaster replies, "I'm even more so, to the point where I can actually feel it when it's folded. So I know exactly where the folds you make will meet."

That doesn't make much sense to you, but evidently, Sans understands. He frowns. "no fair! that counts as weird voidy stuff!"

Gaster snorts, but before he can reply, Undyne interrupts. "THAT WAS FREAKING AWESOME!!" She screams, and proceeds to pester the pair about teaching her, until Sans promptly pretends to fall asleep (or maybe he's not actually pretending and really did fall asleep, you can't be sure) in Gaster's arms, which Gaster uses as an excuse to go home and escape Undyne's excited shouting.

You just wish you had such an excuse, because now you're sure Undyne is going to insist that you train extra hard to use Magic so you and Papyrus and she can all train together to become that good.

§

A/N

Something really important happened in this chapter; some really meaningful foreshadowing. Let's see if anyone spots it.

Anyway, thanks for reading, and I hope you enjoyed it! Comments and votes are my Favorite Things, and every notification I get makes my day!