2Zeratul
The word “partners” is a bit odd. It feels too mundane, too real... I can’t come up with a good replacement yet... maybe it’s not bad, but I don’t like it...

2Dracon Mallasa

Warriors similar to these attacked the elves just today.

We need “warriors.”

Both were approximately the same height, about 180 cm.

Can we define it like this?
Since Silbern is also that tall, maybe you can write –
“both were approximately the same height as him...” ?

One of them held a bloodstained sword in his hand, on which Gothic words were inscribed. Silbern didn’t know the Gothic language, but he was sure it was him. The dead prefer this font.

Gothic? This is the same objection as with “partners.”

Gothic font is a special font, characterized by angular letters, used in Germany and in some other countries.

Maybe you can replace it with –
"strange angular script..."
Or
"unfamiliar angular letters, clearly not Elven and certainly not human... An Elf has never seen anything like it..."

It seems they came to kill someone and quickly disappear. Armor is just extra baggage that would be a hindrance in this case.

“to” together.
And where does this confidence come from that they are going to kill someone specifically? Does the author know this, or is it the elf’s guess? Why does the elf think they came to kill one important person? Why does he think that the armor is not worn precisely so as not to interfere? Maybe vampires are just used to it – without armor...

Both wore long black cloaks, which would help their undead masters hide in the night. The second of those who arrived was also wearing a cloak...

Well, if the first sentence states that the cloaks were on both, then it is unnecessary to write “the second was also in a cloak” in the second sentence. It’s already clear. Write immediately –
“the blade of the second (second) vampire (stranger, creature, non-human) was in a scabbard that was thrown over his back so that...” and so on – the rest is fine.

In his left hand, he held a strange curved dagger, the hilt of which was decorated with a skull, the eye sockets of which glowed with a sinister red light.

The hilt of which, the eye sockets of which... the repetition is not very beautiful.
You can replace it with: "...the hilt of which was decorated with a skull with glowing red sinister eye sockets..."

Or "...a curved dagger with a skull-decorated hilt, the eye sockets of which glowed with a sinister red light."

On the index finger of his left hand was a ring with a green stone, inside of which some shadows were swirling. Silbern was ready to rush at the vampires and avenge the death of his brethren, but he understood all too well the danger. He might not even have time to make a single swing of his blades before the cursed vampire sword pierced his heart. The vampires were so swift in battle.

Uh... where does Silbern get this knowledge of the vampires’ combat reaction speed? Has he fought them a lot? Is this part of the training program at his school? Or did he remember this during the last attack – he saw it with his own eyes... If the latter, which is most likely, this should be indicated. For example, instead of the last sentence:

“Not so long ago, the young elf had the opportunity to see how swift these strangers are in battle. He didn’t want to risk it.

The others had to be on alert every second when fighting these undead warriors.

“warriors.”

The two who arrived quickly headed deeper into the forest.

The comma is unnecessary.

Silbern noted with surprise how silently they moved. Perhaps, in a past life, they were elves themselves, and some skills remained with them. After some time, they all reached Hilael’s palace. Both vampires noticed the archer guard posts before the archers noticed them. They skillfully bypassed these posts, and to Silbern’s great surprise, they began to deftly climb up the tree. They didn’t even break a single branch, so as not to create unnecessary noise! Our young elf also began to climb up the tree, but from the other side. He was scared, because it seemed that these two decided to finish off Hilael. And they stubbornly climbed up to his palace. Silbern didn’t have time to crawl up before the vampires… When he jumped onto the platform, the battle was already in full swing. Our hero, without hesitation, rushed into the battle…

“in full swing” together.
In general, I’m in a state of shock... It’s too easy for these vampires – they got through, climbed up... And no one noticed? Please excuse the author, but it looks too contrived, too simple, and implausible... The vampires practically walk calmly from the edge of the forest, unnoticed, and climb a magical tree... Is it magical? If I remember correctly, it should be enchanted and well-protected. Besides, a battle took place near it recently – so there are many people around... it’s just very strange that the vampires can walk through the whole forest unnoticed...
Maybe you should reconsider the passage? After all, it is quite possible that these two came here with the whole horde, but with a special mission. And while others were fighting and dying, distracting the elves, the vampires sneaked into the inner courtyard of the palace, hid there for a while, and then continued to make their way... And Silbern... And Silbern wandered through the forest and returned to the palace. And... perhaps he stumbled upon a killed (obviously just killed, because it was still quite warm, and the blood was still flowing from the cut throat in spurts)... Perhaps he noticed a shadow slipping past. Two shadows... Yes, he was incredibly lucky that these two didn’t notice him... And, of course, Silbern needed to hurry. It was simply necessary to warn... It is even possible to assume that since the elves won the battle, they are not expecting a new and immediate attack. Perhaps the guard at the palace, on the stairs, is also wounded and helping them. So the vampires could have gotten through...

In general, think about it and rewrite it... Then you will have to revise the first part as well...

In general, this is my opinion-advice, but whether to follow it is up to you...

Sincerely, Simas