It had occurred to her later in the day. She didn't need to ask any pony to submit to her whims. She had a mane! It was a very nice mane. She ran her hoof back through her soft locks. "A very nice mane." All black and flowing... Very nice, she decided, and she could use it for practice as surely as any other pony's mane.
"Oh!" An idea leaped to her and she began scrolling through the, uh, scroll. "Yeah, there..." She was fairly part those letters comprised the 'nature' of the vines she was making. She could... But she shouldn't... She never tweaked a spell like that... But it was her own mane that'd pay the price, not someone else, so...
Umbra grabbed another paper with a glowing horn and got to copying the spell, soon making a second copy with a few minor differences. She slipped in shadowy sigils in the place of 'normal' magic, chuckling darkly as she did it, her sharp teeth on display. "If this works..."
Would the spell even work? According to Starlight, it could be that easy to crudely hack a spell. She was a pro at it! She could kitbash two spells together or warp one into one that barely looked like itself. It was a talent, and one Umbra did not share, but maybe throwing shadow at a spell wasn't past her? She lifted the modified spell up. "Let's try you, on this." She ran a hoof slowly along her mane. "I should take more time to appreciate you." She had nice hair! Er, a mane. Whatever! It was nice.
Hopefully that would continue to be the case.
She cast her spell, shadow leaking from her eyes and horn as she wove arcane runes of shadow together with an excited thrill. It was always... something else when she worked actual shadow magic. She was a shadow wizard. Shadows were her specialty. That made sense, she figured, refocusing on the work she was doing. It was her first time casting that changed spell, so she was taking it nice and slow.
Someone tapped her shoulder. "Eee!" Umbra wheeled around to find a wall. "What?" Something tapped her again. She looked over her shoulder to see a dark tendril of her mane shrinking back as if bashfully hiding. "I see you!" The hair nubbin shook itself as if to say 'oh no you didn't.' "Oh yes I did." She reached for the rebellious lock and nuzzled it. "It worked!"
"Ma'am?" Purple was watching her with apparent confusion. "What worked?"
"This!" She spread her hooves as her mane spread on its own, reaching around the room. With the secret blown, it began to explore and poke at things, wrapped in its veil of shadow. Umbra couldn't feel what it was doing, not directly. When it tugged on her head, that was certainly noticeable, but she could only watch her hair 'sniff' around and explore things with a mind of its own. "Shadow mane! I... think it's alive, kinda... I'm not telling it to do that."
Purple stood stoically still, even as a few strands wafted over her. "Not to question you, ma'am, but what use do you see this being?"
"Well, for one..." Umbra waved back at her new scroll. "It's the first time I modified a spell, and I didn't die, so that's a big plus right there!" She grinned at Purple with sharp teeth on display. "Coulda been way worse."
Purple blinked softly. "We wouldn't want you to be hurt, ma'am. Are you being safe? I could look for another magician to work with you, ma'am."
There were no other magic users about that Umbra had run into... "I'm not calling for some unicorn to schlep up here from Equestria proper just to watch me geek out. No..." She held out a hoof, and they soon wrapped her hoof tightly in her mane. "Hey there... I'll give you some extra shampooing love, just be good for me, alright?"
A glance up revealed her horn was still glowing dimly, holding the spell up. She could cut it off, likely robbing the hair of drive. It wouldn't turn back though... That took a specific other spell she knew. "Hm..." What would happen? Would it go wild and feral like it had been on Purple's head? Her mane was being curious, but not wild. "Hm! Perhaps... it's time for a new jewel." She reached up for her tiara, feeling over it. She had left spots where a jewel could be slotted without making it look odd. She was pretty sure she'd want to expand on it in time. "A nice jewel of shadow mane... Yes... Shadows...." She licked over her lips with a feral satisfaction. "That would be lovely."
Purple cleared her throat softly. "Ma'am, does that mean you desire the company of Shifting Prism?"
"Hm? Oh!" Umbra abandoned her tiara. "Great idea! She's perfect when it comes to picking out these kinds of jewels."
"I will retrieve her, ma'am." And away Purple went, closing the door behind her.
Umbra rubbed her hooves together, only to pause. Around her, several bunches of hair were rubbing against one another in an identical motion. "Are you copying me?" The mane pointed towards itself as if asking 'who, me?' "Yes you!" Umbra chuckled with growing amusement. "I like you, so silly."
She copied her new spell just to wrap it up nice and tight and shove it in a tube. "Starlight will be proud of me. Baby's first magical tinkering." She addressed it with Starlight's face and cutie mark and set it aside for later mailing.
A knocking made her look up. "Hm?"
"It's me." It was Cadance. "Might I come in?"
"Sure!" Umbra grabbed the door in her magic, pulling it free smoothly.
"I just wanted to..." She trailed off, eyes locked on the waving and exploring hair that filled the room. "Is this a bad time?"
"Cadance, meet Umbra-Locks! Umbra-Locks, say hello to the nice pony there." As if listening to her, they came in from all angles, briefly hugging her horn and her neck and her barrel, each time quick, squeezing and exploring the alicorn eagerly. "Isn't it great?!"
"Very... nice..." That she had other thoughts was not well hidden. "Why is your mane doing that? I feel certain I didn't read a story about Sombra's mane doing that."
"Sombra was pretty focused on the whole 'take over the world' thing." Umbra rolled her eyes. "So he didn't do fun things." She reached a hoof out to a hovering lock, petting it gently. "Like a mane with a mind of its own. It's actually shadow-mane. So I guess it had my secret desires."
Cadance colored, but inclined her head slowly. "If it has your secret desires, why is it not... doing anything particularly secret? So far it's been more of a curious dog than anything that might have a secret at all."
Umbra looked left and right, watching her mane play with jars, working them open and closed. They poked and tugged gently at Cadance's mane as if inviting them to play. They pulled open drawers and 'peeked' inside despite having no eyes. It was...
"Oh... Oh no!" Umba began to laugh at herself. "My 'secret' side is my inner child, just soaking in the wonders of the world. Isn't that right?" She made a kissy face at her exploring mane. "You just wanna look around and have fun! If Cadance would play with you, that'd make you so happy, wouldn't it?"
A lock bobbed its 'head' at Umbra. "I had a feeling." She touched her nose to the mane. "Well, up for it?"
Cadance began to smile, some of that mirth rubbing off on her. "That sounds delightful, but isn't what I came for."
"What did you come for?" Umbra sat up straight and her mane went straight behind her, slicked back as if it was always that way.
Cadance recoiled with surprise at the mane so suddenly pulling back to where a mane should be. "Oh, well... To start, I wanted to say thank you. Shining mentioned you'd be watching Flurry for us and I appreciate that so very much. I just couldn't live with myself if I didn't come thank you for that personally."
She took a step forward. "Also... it's not fair that we get a day off having fun and you don't. So after that, we owe you one. You name the time, and we'll cover your duties. That's a fair trade, I hope?"
"How would that work?" Umbra hiked a brow as several locks imitated the gesture as if they were brows. "You're a princess, Cadance. You're busy basically always. Not a mark against you, really, but it is fact."
"Being princess has its privileges... For instance, I know another shadow wizard who would not object to a request for a lent hoof while you relax."
Umbra blinked softly. There was only one shadow wizard she knew of! "Who?!"
"You know her. One Starlight Glimmer. She could take over for a day and let you do as you please."
Umbra squealed softly, hooves shaking in the air as her mane copied the motion. "If she visited, she wouldn't be able to do that, as I'd spend the day with her! Oh, you're visiting Ponyville, right?" She willed the scroll tube into the air and thrust it at Cadance. "Take this with you, please. Give it to Starlight, with my love."
Cadance wrapped a wing around it, holding it close. "I will do just that, and while I'm there, I'll ask about visiting. That sounds like it'd be fun either way, and you deserve it." With that settled, Cadance left. "Excuse me." She went around some other ponies there.
With a squeak, a familiar bat pony rushed into the room. "You needed me?" Purple advanced to silently take her place, ready to leap into action at a request. "She was saying something about a jewel, but she didn't have the specifics. Hit me."
"This day is getting better and better." But her mane was moving on its own, wrapping around a startled Shifting from all angles and squeezing gently. "That's my mane, by the way. Harmless, but very affectionate, curious, and playful. It's all the stuff I usually keep bottled up, unleashed! Behold, my shadow mane."
The mane formed many bulbs of folded hair to 'nod' at Shifting. They were the shadow mane, a title it seemed... proud of?
Shifting giggled, but couldn't move much. More and more hair was ensnaring her. "Is it this friendly with everypony else?"
"No..." Umbra tried to shoo her hair away with limited success. "Hm, maybe it knows we're a thing, and since you're dating me, that means the hair gets to be all personal too."
"I don't..." Shifting considered a moment as her cheeks went red. "If it's you, I don't mind too much..."
"Oh!" Umbra stumbled, tripping right over that kink she happened on. "Um... The hair is not really under my control right now. It has its own brain and that brain is saying, 'yay, let's play! Ooo, look at this funny bat-shaped thing. It looks fun! Hug!'"
Shifting giggled as she tried to wriggle, doing so in the air. The mane had her firmly in its grasp. "It sure is... friendly. Oh, so what jewel did you want?"
"It's related!" Umbra pointed up to her still glowing horn. "I think what makes up the 'mind' of this lovely hair is right now up there. I want to seal that in a jewel where it can keep on living even if I'm, say, asleep or something. And so I keep the same personality. I don't need it to be really angry the next time I cast the spell."
"That would be bad!" Shifting was getting tendrils of hair around her neck. "Very bad... Alright. I can help with that. Now, please, good hair, put me down so I can help."