If we stick to Starhan's version, it's not clear how he was sent on a scouting mission=). Why would someone as responsible and important for Kha-Belekh as this task be given to some transformed elf/human/whatever.

Sareth comes to his senses in a pile of corpses inside a large orc settlement.

Sareth: Oh… What happened?
Xana: Aranthir killed you, and I, drawing a small amount of the Skull's energy... revived you.
Sareth: I feel… somehow different…
Xana: Not surprising. We have merged much more strongly, and now you can even use some of my abilities.

Now Sareth is half-demon, although he retains a human appearance. But at any moment he can become a true demon – with horns, hooves, and a tail. In this case, his strength increases significantly.

Sareth, in demon form, becomes faster and stronger, but can exist in this world only by killing living beings - otherwise, he himself gradually dies. But if allies see him in this form, the game is considered lost.

Perhaps – though there is no certainty – in a similar way Railag "became" Agrail back in the day.

Long ago, in the times of the First Eclipse...

For long centuries, the armies of the Free Peoples fought against hordes of demons. But when they captured the King of the Empire, the human troops suffered defeat after defeat.

Lord Mendes, commander of the royal forces, sent one of his best knights - Sir Evan, to search for the monarch far behind enemy lines. It must be said that this mission was pure suicide, and yet it was not in a knight's nature to question orders from superiors.

And so he set off into the mountains, where he discovered an extensive orc camp. It was these creatures that the Demon Lord had entrusted to guard the captive sovereign, and the orcs treated this command with great responsibility. It is unknown how everything would have ended for Evan, finding himself alone among a multitude of enemies, if not for unexpected help: while wandering near the camp, he happened upon Lorean, an archer from the legendary Unicorn Legion - an elite unit of mercenaries fighting on the side of the Free Peoples' army.

Joining forces, the two broke into the orc camp under cover of night and rescued the King of the human Empire from captivity. However, their deceptively unobstructed raid turned out to be a cleverly set trap; just as Evan and Lorean approached the sovereign, who was held in a wooden cage, figures of orc warriors with flails emerged from the darkness.

The two brave heroes would have met their end here if not for the timely appearance of Kane, captain of the Unicorn Legion. The famous warrior appeared in the form of a giant snow wolf and easily dealt with the now-terrified orcs. The King was free...

After this, Sir Kane convinced Evan to join his unit, and the knight gladly agreed, believing that from then on, as a free mercenary, he could control his own fate and life.

And a few weeks later, the King led the troops in a decisive attack on the demons. The mission of the Unicorn Legion, and specifically Sir Evan, lay away from the main battle - the mercenaries were to penetrate the Demon Lord's fortress through a secret passage and destroy him.

Once again, Evan and Lorean rushed through the corridors of the enemy stronghold, mercilessly slaying orcs and undead that stood in their way. But as they approached the throne room, they noticed their captain - Sir Kane, who had knocked the Demon Lord to the ground and was preparing to deliver the final blow. "What a sweet sight!" the creature groaned mockingly, looking into the eyes of his killer. "My own son is behind all this! And on the side of little humans!" "Don't you dare call me that!" Kane exploded. "You raped my mother! And I never said I was fighting on the side of humans! I will build my own kingdom, and humans are merely means to an end..." "You are doomed, my son," rasped the Demon Lord. "Your thirst for power will consume you. It is already incinerating your soul!"

With a furious cry, Sir Kane plunged his ice spear into the demon's heart, banishing him from the mortal world. Evan and Lorean, hiding behind the doors of the throne room and having heard every word of the conversation, looked at each other anxiously. So, Kane is a half-breed?

The storming of the Demon Lord's fortress was successful. But peace had not yet come to the lands of the Free Nations... nor to Sir Evan's soul. The knight considered it his primary duty to report Kane's nature to Lord Mendes, who received the news with great joy. Of course, if he publicized the fact of the Unicorn Legion captain's demonic origin, the King would undoubtedly exile him from the Empire, and he, Lord Mendes, would become the sovereign's right hand.

A complete surprise for Evan was Kane's order to meet him in the heart of the fortress ruins, which were still swarming with enemy soldiers. What did the commander want?

Breaking through a screen of orcs, undead, and even several Demon Lords, Sir Evan beheld the captain of the Unicorn Legion, standing thoughtfully on the parapet and contemplating the battlefield spread out below. "I need you for a special task," Kane stated bluntly upon seeing the approaching knight. "Lord Mendes has set up his camp nearby. I want you to kill him..." Evan was stunned and could not immediately find an answer. Kill a Lord of the Empire?.. "This lord hindered the rescue of the king from captivity in every way," Kane added, noticing the knight's hesitation. "You swore to protect the crown."

Evan thought: if one considers it, Mendes sent him to the orc camp only to find the king. The monarch's rescue was made possible only by the timely intervention of Lorean and Kane. And yet... "I am a warrior, not an assassin," Evan declared, having reached a decision. "If Mendes is guilty, let him stand trial." "And I am a commander of the Empire's army," Kane cut him off. "And if you are truly a warrior, follow orders!" He turned away, showing that the conversation was over.

Torn between duty and pangs of conscience, Evan headed straight for Lord Mendes' tent, and before the assembled royal knights, accused him of treason. The vain lord merely shrugged impassively and gasped when Evan's blade entered his stomach. The knights gasped: they did not expect such an action from a member of the Unicorn Legion...

But in the next second, the soldiers as one fell upon the lone warrior, and only reinforcements from Captain Kane and Lorean saved his life that day. The archer's ice arrows somewhat dampened the fervor of Mendes' soldiers, and they retreated. Glancing gloomily at Kane, Evan turned and also walked away.

"So you're leaving?" the captain shouted after him. "When victory is so close..." "I'm just leaving, Kane," Evan threw back without looking around. "You know about my origin, don't you?" Kane continued. "You don't trust me anymore, do you?" "I am indifferent to your origin," Evan answered calmly, turning once more to face the captain. "You use people for your own goals, thereby betraying yourself. But I am not your toy..."

Kane launched an attack, and the knights crossed blades before the horrified Lorean. The captain of the Unicorn Legion used all the magic at his disposal, turning now into a wolf, then into a bat, and sometimes becoming a grey mist... But Evan's blade inevitably reached him, and Kane had to admit defeat... for the first time in his life.

Evan walked away, while Kane sank despondently to the ground and did not hear the king approaching him surrounded by a whole squad of knights. "Kane!" the monarch roared. "You deceived me and the entire Empire. There is no place for you here, monster! Do you think that by ordering the death of a nobleman, you served your country?" And he addressed the soldiers: "Throw this traitor into the dungeon!"

Kane did not even resist when the knights bound his hands in chains and dragged him away...

In subsequent years, the King restored his Empire, devastated by war. The soldiers of the Unicorn Legion were declared outcasts and outlawed. Two years after Kane's capture, Evan returned once more to the border of the Empire...

Monsters still abounded here, but now they were not the former knight's only enemies - Evan was also opposed by the soldiers of a small garrison sent by the king to the wild borderlands.

In his travels, Evan met Lorean again. The warrior, stripped of her military status and reduced to the role of a simple bandit, suggested that the former knight try to rescue Sir Kane from prison. After thinking it over, Evan agreed. The scene that had occurred between them upon their parting two years ago still consumed his soul.

But when Evan and Lorean, having destroyed the prison guards and the beholder-warden, broke into the cell where Kane was held, they found the utterly tortured body of their captain, in which a spark of life barely flickered. Suddenly, a Demon Lord materialized nearby and flung Evan far aside with a fireball. "A new era is coming!" the demon proclaimed. "Your civilization will be destroyed by the Dark Heir!" And with these words, the Demon Lord lifted Kane's lifeless body, muttered an incantation, and vanished...

It seemed the demons intended to use Kane in some way to avenge the Free Peoples for their defeat in the past war. Apparently, they planned to perform some ritual on the captain... And Kane and Lorean headed straight for the Hell's Maw, as the residents of the Empire called among themselves the lava-filled depths where Sheog was located - a passage to the interdimensional prison of demons.

Kane struggled to push himself up on his elbows. Darkness surrounded him, an impenetrable and eternal darkness. It had descended since the king's executioners burned out the brave captain's eyes. His dream of creating his own kingdom had shattered into pieces and was now buried in a abyss of pain and despair.

"You need my help!" the slinking voice of the Demon Lord sounded in his ear, but Kane struggled to perceive it, as well as that entire edge of eternal nightmare called "reality". "Their pathetic civilization will turn to dust, and the path to your dream will be paved with corpses! Rise then as the new Demon King!"

"Kane!" Evan burst into the hall with a naked sword in his hand. The Demon Lord smirked, dissolved into the air, and from the shadows of the cave, a huge three-headed dragon stepped toward the former knight.

In that fateful battle, Evan prevailed and, wounded, leaned over his captain. "Evan... I was so angry with you," Kane whispered. "The King was right, as was my father. I am a mistake. A creature unacceptable in this world..." "No!" Evan exclaimed. "You are a person! I understand that now... We owe you so much. You gave us free will and the strength to fight for the future!"

But Kane did not hear him. He was dead.

The demons were cast back into Sheog, but the Free Peoples still have so much to do... Create a new world without endless wars.

Evan and Lorean disappeared once more into the wildlands, setting off on a path known only to them. So many more lessons they had to learn to be sure that they were truly worthy of the hard-won freedom...