( Ok yeah so you just adopted Kronya because she has skills and you are interested of her power and her mind.)
3rd Pov
The Dark Lord in Dul Guldur was then thinking about her Birthday. Y/n the Dark Lord wants to be a good father but he does not know what to give. He then went to Mordor to maybe find a gift in here.
Hours later
Y/n was then at Mordor. He was at his tower and was going down. He wants to talk to his Orc, Urak, and Olog-Hai army about what present does he want to give for her. Y/n then meets with Ratbag and Ranger.
Y/n: " Ratbag!!! Ranger I need your help!!!"
Ratbag: " Ohh my lord what do I, I mean we want from you?"
Y/n: " My daughter's birthday is almost tomorrow and really I need something good."
Ratbag: " Well we Uraks and Olog-Hai have some but it's just the same. We give swords, Dead animals, and other right ranger?"
Ranger: " Oo cha na goroa na ma. ( Yes but I want blood for my foes.)"
Ratbag: " So how about finding another child?"
Y/n: " You mean adopting someone?"
Ratbag: " Yes like whatever you want. Hey I know that sphere thing. It's quite useful."
Y/n thinks that Palantiri is a good idea. Y/n then moved while Ratbag says goodbye to him. Y/n goes up to the tower and looks at the Palantiri. He then touches it and thinks in his mind. He then wants to find someone who is the one that he wants. He then looks to see a vision of the red hair girl that he met before. She then stab a man that he was with the green hair girl he wants. Y/n was then interested but it is then he had visions of the future. He then saw a girl but he thinks it's her. She was then betrayed by a old man. He saw ripping her out so Y/n goes out and turns into hid dark mist form. He then flies to where he can find.
Hours later
A girl named Kronya was then running from Byleth. She ran until she tripped on a rock. Kronya was losing to her while a old man named Solon came. He smiled while he ripped Something in Kronya. It was then Kronya felt pain while she was falling. Darkness was approaching her until another dark mist came fast and caught her. Solon was then confused until the darkness caught Byleth. The Dark Lord Y/n has rescue the girl while a Nazgul came.
Y/n: " Take her to Mordor while I take care of him."
The Nazgul then grabs Kronya and ran to Mordor. Y/n looks at the man who killed Kronya and then turns into his mist form. Y/n then faces the dark mage.
Solon: " A dark mist well begone!!!"
Solon uses his dark magic until Y/n absorbs it. Solon uses a lot of his dark magic while the blue lions sees it. Darkness fighting darkness. The two class until Solon uses more dark power. It was then the black mist then told him.
Y/n: " Fool."
It was then a dark mist then reveal the great terror that no one never saw for a thousand of years. It was then Y/n in his armor form then made his symbol.
( Song On)
Dimitri never thought it was something that dark of horror. The students felt fear in their bodies. Something that the shadows that appear. Solon stands but fears that the power of his darkness is somehow absorbing him. The dark lord now revealing it self then felt the world in fear. Far away Rhea then sense a dark power while where far a vault inside was then glowing. Y/n then walks out of the eye while on fire.
Y/n: " You think you can use her as a weapon. I'll punish you."
Solon: " I am not scared of you!!!"
Y/n: " Ohh old man you should be."
Solon uses his dark magic but it only made Y/n stronger.
Y/n: " Ohh old man you making me stronger here let me give you my power."
Y/n throws his dark magic at Solon. Solon got hit but he felt more power in him. Solon then laughed and felt his power.
Solon: " This is interesting!!! I felt no power that I ever thought!!!"
Y/n: " I see but can you hold it."
It was then darkness was eating Solon. He was then panicking that no darkness will not obey him. He then was eaten by darkness and absorbs in Y/n. He felt more power while the students got out their weapons. Y/n then turn into his armor while he was not on fire.
Y/n: " No one will help you. There is only darkness."
It was then a sword was then cut. Out from the tear was Byleth. Her hair was then light green until Y/n looks at her to see she might be related to his enemy.
Y/n: " Ahhh it's good to see the daughter of my old enemy."
Byleth: " Who are you!!!"
Dimitri: " Be careful Professor!!! He's stronger and dangerous!!!"
Byleth ready her sword until Y/n knows her fighting pose from someone. Y/n ready a his mace until Byleth turn her sword into her chain. Her sword glows and slash Y/n. Y/n felt a little pain due from the sword was ancient. Y/n swing his mace at her but dodge.
Y/n: " You are smart but I'll take what you stole."
Dimitri: " What are you talking about!!!"
Y/n: " Nothing but this time you will die!!!"
It was then Rhea came and had a white ring on her. She uses it and made Y/n weak.
Rhea: " You have no power here!!!"
Y/n: " No I am stronger then you!!!"
Rhea: " You will go back to Mordor!!!"
Y/n: " No my friend it is you to back to darkness."
It was then darkness came and 9 Green mist appears. Out from the mist was ghost men with swords. They where here to kill Rhea.
Y/n: " You should not go alone."
It was then a man who is a elf and a man with white hair. Elrond and Saurman appears to see the dark lord alive.
Elrond: " Y/n I knew that you are alive."
Y/n: " I know you. You where in the fight and let me guess. Rhea is not who she is."
Rhea was then silent until the Nazgul then attack her. Elrond and Saurman then was defending her while the Nazguls slash them. Saurman uses his staff and bash them. Elrond then slash and stabs the Nazgul. The Nazgul disappeared and turns into mist. Y/n was then got out is mace until Rhea uses her ring and weakens Y/n. Y/n then had no choice to go back to Mordor. Rhea looks at Y/n running while Elrond and Saurman where silent.
Dimitri: " Who was this man and why does he know you!!!"
Elrond: " There are a lot of things to know about the secrets that no one knows."
Elrond left while Rhea was then talking to Byleth. The white wizard Saurman felt more power from Y/n so he then wanted to know knowledge about him. At Mordor Y/n was in Mordor while the witch king and the 4 nazguls where helping the girl. The Witch King came fast so he can heal her. She suffer from blood leaking but she needs a new heart. The witch king then got a heat from the girl who betrays them. The witch king then put her heart in her.
Witch King: " My lord we need blood if we can save her."
Y/n then took out his gauntlet and reveals his flesh hand. The Nazgul gave him a dagger an dab Y/n slash his had. Blood then came out of his hand and put in on a large cup. The Witch King then put the cup on her mouth and let's her drink it.
Witch King: " Yes!!! Now my girl. Ohh cha go ma na ka Chogo na ma go!!! Raise the second daughter of the Dark Lord!!!"
It was then a dark aura was then regaining a new power in her. Kronya was stabilize but she needs to rest. The Witch Kong then left to go with D/n while Kronya was then taken to her bed put the tower. Y/n then was in the tower looking around on Mordor for any issues. Kronya was now the second child of the dark lord Y/n.