An inverted shadow rune hovered above Umbra's head, emitting a mysterious and ethereal luminescence. "This is to weaken, draw, and defray. Applied directly, it saps at the power of whatever you're aiming it at. The stronger the thing you're trying to sap, the more effort's needed." With pops of magic, she summoned blocks of crystal. "We'll target these. Because they are rocks, we won't hurt them, nor will we make them complain."
Taking into consideration the crystal target and the rune she could sense Umbra was casting, Cadance thought carefully. "First, how could this have a positive end? That feels fairly... straightforwardly 'bad'."
"Fine question. First, defense." Umbra pointed at Shining. "As nice as hiding behind a shield is, if you can weaken what's battering against it, that's a bonus, yeah? Less effort into keeping the shield up. Imagine how much easier it would have been if every time the jerk came knocking, you gave him a zap with this." A feral joy spread across her face as her head filled with the images of the scene unfolding. "That would be great."
Shining thoughtfully considered the idea, emitting a soft hum as he did. "Yeah... Alright, I can see that. If I could weaken that mass of changelings that one time, that would have been pretty great... if I was thinking straight." The recollection of that memory caused him to furrow his brow in displeasure. "Let's not get too far into that. Alright, so, using it in a fight, I get that... But if you're not fighting?"
Umbra met shining with a teasing smile as she said, "Sometimes, even the lightest of ponies... Even they need to get through something. Stubborn vines, tough rocks, or anything else you need to get out of the way. Setting it on fire is an option, or trying to make it vanish, but both have their own issues. With this, you can weaken it, then give it a good pull and it'll tear free."
Busy in her endeavor to recreate the rune that Umbra had already showed to her, Cadance was working hard. "Like... that?" She pointed up at her darkly glowing horn. "Is that right?"
Umbra shook her head. "Close." She focused on the rune, emphasizing the internal muscles that held the rune in shape. "Like that."
"Like this." She copied the feeling, and the rune, glowing above her head. "There... we go... Now, aim!" She glared at a crystal, eyes flaring with the shadow power Umbra had by default. The crystal trembled and shook as if struck by the magic. "How do I know if it worked?"
Umbra brought up her hooves towards the crystal. "First, you have that whole dark field around it. That's a clue." It shone with the dread power of darkness. "Second, fun part, you just try to tear it. Attack it. Go on, vent your fury on it."
Cadance let her tongue peek free a little, concentration on her face. "This... Shining, you go ahead."
"Alright." And he began working on the rune, only to be swatted on the back. "What?"
Cadance indicated the crystal with her hoof. "Break it."
"Oh!" Shining scrambled to the crystal with a clatter of his hooves. "And chop!" He brought down a hoof on it to discover rapidly that it was still a rock. "Ow..." He held the hoof close, nursing his bump.
"Very good." Umbra patted the badly bruised stone. "Shining could not, normally, do that so easily. This is also why crystal works pretty well as a test, since you'd have to get great at this to have people just tearing it in half."
Cadance abandoned her magic to help comfort Shining. "I didn't realize..."
"It's alright... You get the next one." The magical swirl caught both their attentions. The untouched crystal was glimmering with dark warnings of foul magic. Tracing it back, Flurry was glaring at it with all her immature potency, surging wildly in a fit of shadow magic.
"Look at you!" Umbra applauded at the sight. "My lovely niece, already showing we're related. What a field... I bet that crystal's as soft as clay." She went to test that, stepping on the block and pushing down. Instead of the stone being hard and firm, it was as if her hoof was sinking into chilled butter as she placed pressure on it. "Look who's a talented little shadow wizard!"
Without any announcement, Flurry decided that Cadance's hoof was far more entertaining than what she was previously doing, and so she stopped to play with it instead. This did not prevent Umbra from taking her in her arms and giving her a loving squeeze. "I am so proud of you I don't even have words!"
Cadance smiled at the exchange. "I don't think I'll tire of that. You have a deep and genuine love for her... This may be the romantic in me, but it's a lot easier to love ponies who love my child."
Shining let out a gentle, yet amused chuckle. "That's pretty normal, Cadie. Most ponies don't get along with other ponies who don't like their kids. Now... I don't want to be shown up. I'll get this." He looked at the unharmed crystal, focusing on the new rune. "Give me a moment..."
She swatted at him, though she didn't make contact, or really try. "Besides that. Whatever Umbra has done wrong before, she's never failed as an aunt, or a mother, for that matter... That counts. Your daughter, son, and niece are fortunate to have you there, supporting them with all of your heart. Shadow or light, you are ready to embrace them tightly and be there for their triumphs and troubles. That... means a lot to me."
Shining's frown grew slowly with time as he concentrated on the rock. "Speaking... of that, how are they?"
Cadance clapped. "Oh yes. Your son is a darling pony. I hear his talent is the sun? How marvelous! Like Celestia? You must be amazed."
"Not like her." Umbra glanced up at the evening sky. "The sun will remain in its place regardless of his efforts to move it. I hear that's very hard to do for many besides Celestia. But! He can focus its light, gather it, and move it around. He puts the light in pony. You're all light aligned, but he takes that to the next level. Very proud of him." A smile spread across her face as her thoughts wandered to Anik and the amazing and bright magic he possessed. "Fitting of an earth pony. He could make things grow, or set fires."
Shining flipped an ear back. "Glad he's not focused on—Oh! Here!" He pointed to where the dark shadow had formed around the crystal. He was doing it, throwing out that weakening field. "Try."
Umbra stepped up onto the crystal, placing all her weight on it. It sagged, not as easily or quickly as when Flurry had done the same, but that it had weakened was clear as she sank into it. "Nice, nice! One thing, little thing. If you were an enchanter, which neither of you are, this sort of thing? It ruins a crystal's enchantability. Forceful deforming like this? Nope! They hate it."
Shining slowed his magic to a stop. "That sounds... bad. Why are you having us do this, then?"
Umbra kicked the unfeeling slab of crystal. "This was already low quality. You're lowering it from junk to junk. If you do want to work a crystal you plan to enchant, you have to be way more careful than this. This is a brute force method. On the other hand..." She rolled a hoof she had instead of a hand. "If you just need to break through something or tear something down, this'll get you there.
Cadance smiled radiantly. "I get it. These are still just single letters. We can't expect too much."
"True..." Shining tapped at his chin. "Alright, we got two letters. I'm going to guess the next step is to practice them."
"A lot." Umbra nodded firmly with a soft snort. "Until you're tired of it, and can make the letter without thinking about it. You, Shining, already know a lot of letters. Just as good as the rest. While you're doing that..." She grabbed Flurry in her magic and levitated the wriggly filly up onto her head. "I'm going to steal your child and love her, maybe to death. Her death or mine? We'll find out. Better act fast."
Cadance crossed her arms in front of her chest. "I will learn to enchant if I have to and stuff your ghost in something to torment you forever if you go and die in front of Flurry Heart."
"Ooo, nice warning." Laughing, Umbra trotted off with her victim, er, niece, the two sharing a smile with one another with radiant joy between them.
Shining rubbed at his cheek. "Huh, well... First night out with Umbra. That wasn't bad, and we learned something."
"We did." Cadance inclined her head at Shining Armor. "But you sound disappointed. Is something wrong?"
"Fun time rarely comes with homework." He showed his disapproval of the current state of affairs by extending his tongue in dismay. "Not sure I like that part."
Cadance brushed against him, walking past. "Let's get these put away, maybe somewhere to practice later." Her horn glowed, dimming the area around herself. "We can practice the shadow one easily enough anywhere. We have a shadow wizard for a fiancé, the least we can do is show some interest in her passion."
Shining willed the slabs up with his magic, hovering them there in the air. "This is easier for you to say. She'll be helping take the pressure off you."
"You know, if you asked, she'd jump on your guards and show them a thing or two." Cadance was filled with amusement when she pictured the situation in her mind, bringing a smirk to her face. "She can be a tough leader when she wants to be. You two were quite the formidable pair when the umbrum attacked, don't forget."
"Probably, but that isn't fair either." Shining started for the palace with his two big presents. "She has a life too. I can handle the guards."
"You do a great job with it." The glow around one of the slabs shifted as Cadance took mental control of it with her own glowing horn. "Now, if we're being honest, I'm curious what kind of O&O game she'll run... and I want to learn the rest of her 'wicked' magic."
Shining hesitated briefly. "Really? I didn't think you'd be that interested."
Cadance rolled her eyes. "This is why I know so few letters. Umbra wants to teach me, and I want to learn. What's the point of having this thing." She pointed up at her horn firmly. "Without even knowing how to use it?! Float things around, and do my cutie mark's magic? Talk about bare basics... I can do better! I'm Twilight's sister! I can't go embarrassing her like this."
"In--"
Cadance struck him over the head with a dull thunk of her hoof meeting him. "Don't even finish that. Is it any better that my old foalsitted foal is showing me up like this? No! I will get better, and Umbra wants to help. I may never be a proper wizard, but I will learn to read and cast a spell properly."
Shining rubbed the sore spot. "Alright alright! I just didn't think you... cared much about that, is all."
"Then maybe you don't know everything about me." She sped up into a proper trot, vanishing into the throne room. The door closed without obvious source a moment later.
Shining stood there for a moment, looking at the closed door in contemplation. "Huh... Then I should fix that."