The Reason Why|Yveltal x Xerneas!Reader x Zygarde

I was simply minding my own business, wandering around the base of the Yggdrasil Tree. It was my duty to protect the soil, to keep it preserved and lively.

"You ever get tired just prancing around day and night, Xerneas?" Looking up, I saw large black and red wings come into view. Then I narrowed me eyes as Yveltal appeared before me, his blue eyes reflecting some degree of smugness.

"Don't you have things to destroy, birdie?" I huffed, turning around.

"Well, you'll just bring them back anyway, wouldn't you?" Yveltal flew over, blocking my way as his face became merely inches from mine. "Because you claim that you're "doing good". But the real question is...are you doing the right thing?"

I simply sighed. For thousands of years we've done this same song and dance: life verses death; creation versus destruction...we were polar opposites, at the opposite ends of fate. We never agreed on ANYTHING.

"Like you're one to talk," I growled, stomping my hoof, "I make life and all you do is take it for your own selfish needs! Maybe death is the only way to keep balance in this world, but there's a limit."

The red bird simply gawked at my statement. "You..you fool!" He screeched. "Look at us! We are Legendary Pokemon! With limitless power! We can do anything we plea-!"

"Hey, what's with all the noise upstairs?" Glancing down, I saw Zygarde (his 50% form) appear up from the ground, looking at both of us curiously. We rarely ever saw him, since he was always underground monitoring the ecosystem. He may have heard bird-brain and I arguing before but this was the first time he actually intervened.

"I swear, you two argue like a married human couple.." Zygardge remarked, shaking his head.

"Don't ever compare me to such creatures!" Yveltal hissed, glaring at the snake-like Legendary. "We weren't made to be captured by those inferior beings for their own amusement!"

"That is true," I nodded, scraping at some of the dirt with my hoof. "We were made to be free Pokemon, so we may keep order in this world. But.." I looked over at Yveltal. "I wouldn't go as far as to say all humans are inferior. Many of them, namely Pokemon trainers, have potential. Some have even captured.." I paused for a moment, looking up at the night sky.

"...a few of our own."

"You can't be serious!" He gawked once more, his eyes reflecting disgust. "How could our own kind even stoop to such a level?! All this power and they decide to become human pets?!" He spat out the world like venom, before sighing angrily.

"I swear, one day I'm gonna use my Oblivion Wing on those humans, Xerneas." Shaking his head, Yveltal turned around and spread his wings, taking off into the sky and back to his nest in the sacred tree.

"You aren't gonna let him do that, will you?" Zygarde asked me. I sighed, sitting down in front of him. At that point, I just needed someone to talk to..though the only being I've ever talked to was Yveltal. "No. Yveltal wouldn't be foolish enough to use that move. He's not as strong as he gloats to be."
"Well, you two may not get along, but there's a reason why you and him were embedded with these century-long feelings of spite and hatred."

"Oh?" My ears perked up. "Why is that, Zygarde?"

"You can't have life without death, right?" He tilted his head. "And vice versa?" He tilted his head the other way, amusing me slightly.

"You're right, but we already know-"

"But what you both don't know is where to draw the line," he pointed out. "You and Yveltal can't reach an agreement without destroying and reviving the forest. You may always fight him, but one cannot live without the other. Without any Xerneases, there would be only be destruction and chaos, which is not good for the ecosystems. Without Yveltas, nothing in this world will die and it will overpopulate and hurt the ecosystems as well."

"Huh..you speak wisely, almost as wise as an Arceus," I chuckled. "I suppose you are right. Even if Yveltal acts like a spoiled Pokemon we still need each other...I am sorry for all the trouble we've caused you." I bowed my head to nuzzle my nose with his.

"It's quite alright," he replied, nuzzling me back. "It's nice to pop up once in a while to see my friends and our beautiful tree." Zygarde gazed past me, towards the white, glowing tree in wonder. "Speaking of which..I must tend to my duties. I'll see you around, Xerneas."

I nodded, smiling slightly. "Farewell, Zygarde." Nodding back, the snake-like Legendary disappeared back underground.

I guess I was wrong about him: a Zygarde does, indeed, fit into the cycle. But should Yveltal and I ever fight again, which is bound to happen for many years to come, I'll be sure to keep the guardian of the tree's roots in mind.