Just seeking some useful critiquing. Things are purposefully vague, by the way, and they will be explained in later chapters. This is also a prologue.

The moon, full in its glory, lingered over the shadowy castle. Its light cascaded hauntingly into the ballroom, making the red splatters scattered among the marble floor shimmer. It was beauty among the ghastly; crystalline in its form. Zane cast a bloody hand upon the wall, pulling his weak self up until he finally stood. A single, thin cut shown on his cheek and his otherwise extravagant clothes were drenched with the tears and blood of his relatives. He was deathly pale and frightened. Attempting to step forward, the man leaned against the wall, only to trip on a lump of cloth. The prince swore beneath his breath as he lay over the object. "Damn..." he stopped with his hand midair, ready to strike whatever it was in frustration.

It was only when he realized it was the body of a small boy when he hesitated. And it was only when he realized it was the body of his brother, Samuel, when he screamed and crawled back. All he wished was for this hellish nightmare to end quickly. Somehow, he expected to wake suddenly and find that it was all a cruel dream. He imagined himself creeping exhaustingly down the steps to the dining room to meet his father, brothers, and Ari waiting for him as they sat around the table. He knew that couldn't be. He wanted it to be, but it couldn't. Everyone had gone away now and nothing could be done...except it wasn't everyone. He remembered, quickly standing and sprinting towards the ballroom door, his mind frantic. The man's heavy footsteps echoed through the halls as droplet after droplet of blood dripped from his clothes to the floor. The hall spun around him as he reached for the glass doorknob and turned it, blasting into the room. Aminri faced him, calm at first, but when he saw the tattered man his eyes widened and he screeched, "What happened to you?"

Collapsing against the wall, Zane held his aching arm and replied, "Soldiers... there were soldiers, my father's soldiers..."

"Yes, what about them?" The smaller man grasped Zane's shoulders.

"They stormed the place with guns and blades, things my father had given them, my dead father, who they swore loyalty to. Is that what soldiers do, Ari? Do they first appear as the strongest army, having undying faith for their leader, only to turn around and kill his family after he takes a bullet to his--the gods, Ari, what's happened to us?"

Zane slumped to the ground and dug his face into his knees, as if hiding from the world. Aminri only looked at him for a moment, then whispered, "What's happened to the royal family...?"

"They're dead!" he snapped, "They're all dead! Samuel, Father, Helena..."

"Howl isn't dead, Zane."

"Oh, Howl! He's dead alright. So dead, he's alive! And soon that fate will follow you and me!"

Aminri grasped the crazed man's arm, fearful. "Zane, you're not making any sense, please..."

The door swung open and in thundered a soldier, clad in black. Although Aminri was holding him back, Zane stood and faced the intruder. "So? Are you going to kill me as well?"

The soldier was silent, standing there, gun in hand. A silence loomed over the room. "Come on, then, shoot me. Or are you too much of a coward?"

Still, the soldier was silent, standing as if he was deaf to the man's words. It was only when the echoes of the other soldier's voices cam closer and closer to the room. Hastily, the soldier cocked their gun and aimed it at the two.

So I’d put this on my list of things to critique way back when you posted it. God knows why it took me so long to get to. I’m glad I finally found some time to critique it!
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Originally Posted by wellel

…making the red splatters scattered among the marble floor shimmer.

I’d use ‘scatter’ instead of ‘scattered’.
By starting the sentence with ‘making’ you make the tense of the sentence present, while ‘scattered’ is past. So either ‘scattered’ needs to be ‘scatter’ or ‘making’ needs to be ‘made’. It depends on the tense you want to use.
Using past tense would match the rest of the piece, but for artistic license, you could probably get away with making this once sentence present.

Originally Posted by wellel

…pulling his weak self up until he finally stood.

‘his weak self’ doesn’t seem to have the profound effect on me I think this sentence needs. Something about the word ‘self’ here seems almost… humorous. Maybe it’s just because I cam from the generation that loved ‘my bad self’ so much. Hah.
You might change ‘self’ to ‘body’, though.

Originally Posted by wellel

A single, thin cut shown on his cheek…

‘Shown’ doesn’t really work well here. Laid? Bled? By using ‘shown’ it seems like he should be showing it to someone and since he’s not I feel like it doesn’t sit right.

Originally Posted by wellel

The prince swore beneath his breath as he lay over the object.

I know you’re trying to call him something other than ‘he’, and I commend you for it (so many people don’t bother), but using a title like ‘the prince’ could be hinted at earlier. Is this room a throne room? Does he have a crown on? Is his crown missing? It’s not a necessary thing, but it might be worth playing with.

Originally Posted by wellel

… body of a small boy when he hesitated.

The ‘when’ here should be ‘that’. ‘That’ makes it a reason whereas ‘when’ is just a time. So ‘when’ is the time he realized it was Samuel; ‘that’ is his action of hesitation. I hope I explained that okay. =\

Originally Posted by wellel

… when he screamed and crawled back.

‘that’ instead of ‘when’. For the same reason.

Originally Posted by wellel

Everyone had gone away now and nothing could be done...except it wasn't everyone. He remembered, quickly standing and sprinting towards the ballroom door, his mind frantic.

I’d put ‘he remembered’ into the same sentence as ‘except it wasn’t everyone’, since that’s what he remembered. I think these two sentences could be restructured to flow a little better:
“Everyone had gone away now and nothing could be done… except it wasn’t everyone, he remembered. His mind frantic, he quickly stood and sprinted towards the ballroom door.”
Or something along those lines. I had to switch some tenses to make that particular edit work, but you get my drift. In what you have now there just seems to be a lot of fragmentation that doesn’t need to be there.

Originally Posted by wellel

"They stormed the place with guns and blades, things my father had given them, my dead father, who they swore loyalty to.

This really depends on your character, but this seems to be exposition that would better be explained in a different way. It just feels a little like the character is feeding us exposition instead of really and honestly freaking out to his friend(?). Again, it really could be just the way the character talks, but I thought I’d point it out in case he doesn’t talk like this throughout the entire story.

Originally Posted by wellel

It was only when the echoes of the other soldier's voices cam closer and closer to the room.

‘came’ instead of ‘cam’, just a little typo. And “soldier’s” should be “soldiers’ ” Because it’s the possessive form of more than one soldier, the comma goes after the ‘s’.
It was only when what? I think you should combine the last two sentences:
“It was only when the echoes of the other soldiers’ voices came closer and closer to the room that the soldier hastily cocked (his or their? Is there more than one soldier aiming at the prince?) gun and aimed it at the two.”
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Overall you seem to have a good grasp of balancing description and action. Neither felt over or understated. There were a few grammatical issues, but nothing that really deterred from the story. The only thing I’d watch out for is some word choice. The right word can real make a sentence pop.

I hope I was of some help and I hope you get more of this written. I’d really like to know what happened and I quite like the prince already.