Art done by  PyroPaws

(Part of an UNDERTALE/Zeydaan AU where Zeydaan gave a chunk of his soul for Asriel to live, making him a monster in the process.)

Zeydaan woke up Asriel quietly in the middle of the night. The young prince stirred and soon smiled at his brother.

"Happy Birthday, Azzy," he said with a grin, but trying not to speak too loudly to wake up Toriel. Asriel slipped on his shirt to cover up his fluffy chest.

"Happy Birthday, Zeydaan," the young boss monster said just as quietly. Slipping a small wrapped package under his jumper before Zeydaan spoke again.

"Ok, I promised you something cool and big for your birthday, I've thought of just the thing." Zeydaan beckoned him across as he leapt out the window. A ladder soon floated up onto the balcony, Asriel got the idea quickly.

Zeydaan's fur wasn't as thick as Asriel's nor was his suit as insulating as Asriel's sweater. But he knew the walk wouldn't be far. He slipped some gloves onto his paws before he felt the gentle hand of Asriel on his.

"Where are we going?" Asriel asked.

"It's a surprise."

It was dead of the night, and Luna's moon was shining a gentle silver light. It wasn't long before they arrived where Zeydaan wanted to go. Mt Ebott.

Asriel was confused, but knew Zeydaan would do stuff like this for him. Zeydaan held on tight, and the two quickly floated up to the top, where the opening was.

Asriel's expression dropped when he saw what awaited him and Zeydaan down in the hole, the entrance to the old Underground. Where once a small group of flowers grew was nothing but a few greyed corpses of flowers. Zeydaan had the same expression as well, scratching under his eye as Asriel looked up to him.

"I'm sorry, I didn't mean for it to be like this. I planned for us to have a midnight picnic at the place I met you first... You know, for Nostalgia."

They looked at eachother for a moment, Zeydaan smiled at him. "Can you believe that was 10 years ago?"

"Not really, you grow up quicker than I do, I guess time flies for you" the smile was returned. "It's alright if it didn't turn out how you wanted it to... The gesture's nice. These wouldn't have survived without the monsters down here, someone's gotta take care of those flowers."

The smile of his brother filled Zeydaan with Determination, he had an idea.

"How's your magic practice going?" he asked offhandedly.

Asriel stood up, looked at a wall and shouted, "Star Blazing!"

A single star dinked off the side of the rocks and landed on the ground. Zeydaan gave an encouraging clap. "You're improving, definitely. That one definitely didn't backfire... But for what I'm planning on doing is going to require a bit of energy from the both of us. You want to try?"

Asriel nodded as Zeydaan walked up to him and looked at him directly in the eyes.

"Now, what I want you to do is think of happy thoughts, lots of them. It doesn't matter what they are or where they're from, as long as their happy memories. Can you do that."

Asriel scrunched his face and paws, and nodded sharply. "Mm!"

"Great, now hold them in your head as much as you can, try not to wander, just keep them happy!"

Zeydaan focused his magic, getting a little stream into his 'brother's head through the section of his soul. It was a simple restoration spell, enough to get a nice patch of Flowers. He'd siphon off a bit of Asriel's positive energy to get enough white magic energy for the spell to work properly.

The little monster was scrunching tight and closing his eyes. As soon as the Siphon hit Zeydaan's systems, he felt the burst of what was going through Asriel's head.

From seeing Zeydaan once more after shattering the barrier, seeing him as a friend rather than an enemy for the first time. The way that Zeydaan, as a young human, shattered his soul willingly and gave him a section, the equivalent of a monster soul. But it wasn't the process of what happened, it was when Zeydaan looked up at him, reborn as a monster and hugged him as a brother. The way their parents reacted to seeing Asriel alive once more, the ten years spent on the surface world- it was almost too much for Zeydaan, so he quickly used his spell on clenching his eyes shut.

The two of them opened their eyes at the same time, to see that the spell had worked.

Although a bit too well.

It wasn't just a patch of flowers that had regrown, but circling out from both of them was a dense cluster of golden flowers that spread out across the floor and up around the walls, down the long corridor, and even some had made it to the top of the hole. Asriel gasped in delight as some of the Flowers gently fell to the ground, Zeydaan reached out his paws and caught one of the smaller ones as Asriel laughed to himself.

"Wow," he said quietly. "This is wonderful."

Zeydaan looked at his friend and his brother with a smile. "Such... Beautiful magic, eh Asriel?"

"Thank you!" the boy shouted excitedly, tackling his friend to the ground, crushing a few of the flowers, causing laughter from the both of them.

They did not have a picnic that night, but instead just lay on the flowers as the gentle moonlight flowed through the hole onto the both of them, Asriel reached under his top and took out the small package that he had had.

"Mettaton made this, I hope you like it."

Inside the box was a jewel encrusted badge in the shape of the delta rune, the Dreemurr family emblem. Zeydaan's eyes widen. "It's not much, but-"

"I love it. This means so much more than you know to me. Thank you so much Asriel."

He looked proudly at Asriel, clipping the badge over one of the pockets on his suit, and although he didn't want to admit it, he was holding back tears.

---

The two lay on the ground for a little while longer. "I'm sorry I overloaded the spell. I'm glad the results didn't go badly," blurted Asriel in a way that seemed to say that was on his mind.

"No need to apologise. I just didn't expect so much... I gotta admire your guts, you've been through so much, yet you're able to harness all that positive energy into something like that, that's not something I can do easily. How do you do it."

Asriel turned while lying down to meet his gaze.

"Magic," he joked, causing a chuckle from the both of them.

They held paws for a while, Zeydaan's completely cupping Asriel's smaller one.

"Can I ask you a question?" asked Asriel.

"Sure, bro... What about?"

"You said you admire me for keeping positive despite everything... Why do you say that?"

Zeydaan held more a neutral face and breathed the cool night air deeply. He gazed up at the moon.

"Trust me, Azzy... It's a long story."