As always I own nothing of Tolkien or his works. It will not be 100% lore compliant, but I do respect the lore with all I am. I will do my best to treat it as well as I can.
The daughter of Denethor
Dinenthel was the second child of Denethor and his wife Finduilas. Born in 2980 of the third age of middle earth. From a young age, she followed her big brother Boromir and little brother Faramir like she was stuck to them. Even if they had classes in warfare and sword fighting she snuck along as she had no interest in her own classes to be one of the ladies of Minas Tirith.
Every time she came with them Denethor or Finduilas took her back, but not even 10 minutes later she had left and snuck back into Boromir and Faramir's classes she excelled at them and one day she managed to convince her father to listen to what she had learned.
"So Dienethel, if our front line goes straight like this and Mordor charges the whole front line with orcs and wargs. How would you repel them?"
She sat there looking at her father and the Captain of the citadel guard setting up the battlefield.
"Would my force be outnumbered?" She said asking one of a few questions she was allowed.
"You will always be outnumbered Dienethel. Mordor and its allied forces are numerous, but they lack our skill at arms" Her father told her.
Thinking some more she grabbed a few pieces of spearmen and swordmen.
"I would put the spearmen in front, with swordsmen just behind them." She started to explain. Her father and grandfather watching.
"Then I would keep some forces in reserve here to reinforce the line where needed and archers to cover the front lines and attack any troll or warg coming at us. As well as thinning the infantry line." She explained. Denethor just stood there listening.
"Very well," he said after a while. "What of our cavalry? how would you use them?"
Looking over the battlefield she separated the forces of cavalry.
"I would separate them into two groups." She said "One to flank on each side of the front line holds and tear up the lines of Mordor from each side" showing them how it would happen.
Her father looked at the table and her tactic for a bit and told her to go into the hall and wait there for them to call her back in.
"What do you think, Herhold?" Denethor asked the Captain.
"Her tactics are sound my Lord. She is as eager in classes as her brothers and would make a fine addition to our forces." The Captain explained.
Denethor listened and looked over the table once more. "But she is but a woman not meant for the battlefield. She is meant to get married to a Lord and give us heirs." Denethor let out upset at his daughter's stubborn will.
"If I may My Lord" The captain spoke and Denethor nodded to him. "She will never stop running into my classes with Boromir and Faramir. The blood and pride of Numenor are in her and that is not something we should try to extinguish today. The southerons pushes on our southern border. Minas Morgul is not dormant and what knows what forces Rhun is sending to Mordor?"
As Denethor and Herhold were talking over the matter Dinenthel was sitting outside the office of the steward and waiting on her judgment as Boromir and Faramir came to her.
"How are you feeling little sister?" Boromir said in his warm and protective brotherly way.
"I am fine, but I don't think father will ever let me join your classes with Herhold" she responded sadly.
"Chin up big sister," Faramir said with his ever-positive attitude. "Herhold does let you sit in, doesn't he? And we will support you too. Even if you come up with better answers than us at times" her little brother said.
Dinenthel looked at Faramir and let out a cheeky "Some of the time? As far as I remember Faramir I do come up with better answers than you mostly and sometimes better than Boromir" she grinned.
"Key word for me is sometimes," Said Boromir proudly "It is not as bad as you make it seem," Faramir said proudly
"You two really think he will let me fight?" Dinenthel said after their banter had died down. "Father has changed after mother passed" Boromir and Faramir looked at their sister and her faces showed a desperation to be allowed a life of a warrior of the white city.
Her brothers looked at each other and then at her, each of them grabbing a shoulder.
"If not sister we will find a way," They both said confidently and proudly.
At that moment the doors into the offices of the steward opened and Herhold told them to enter. Denethor sitting by the table looking it over yet again.
"Dinenthel, come forward," he said commandingly. "I Denethor, steward of Gondor and the high king, lord of Minas Tirith accept your wish to become a student of Captain of the citadel guard of Minas Tirith. But hear this. At any moment he deems you unfit for any reason to be a warrior, captain, and leader of our armies you will stand down. Be stripped of your rank under the banner of the white tree and go back to any role befit a woman." He said as he drew his sword and made her swear an oath on it that she would accept it if it were to happen.
"You made it" Boromir and Faramir screamed in happiness and celebrated as soon as they were all excused. She could not believe it. After their mother died their father had become dark and withdrawn as well as looking down on her and Faramir, but this day glimpse of the old loving father that only wanted his children happy had returned for but a moment.
"I cannot believe it." She said. Happiness was printed on her face. "I cannot thank you two enough for supporting me and my dreams" she giggled and hugged them both so hard. She knew life would be tough, but if Faramir and Boromir could do it so could she. The three children of the steward stood in the hall, all excited as Herhold also excited the steward's office.
"My lady Dinenthel," He said and bowed his head a little. "If you come with me, we need to go to the smiths and see if they can make you a sword and armor to train in." Her smile was huge. It would not be full plate armor as he wore or the other soldiers. But it would be one day. As she and her brothers followed Herhold to the smiths they waited on her to get measurements taken.
It would be mostly a hauberk, the white tree on her front, leggings, vambraces, and a helmet as all the soldiers wore. Hard steel helmet with good protection of the head and only open in the front and slimed into a pointy part on the top. Just like her brothers.
After that, it was back to the Citadel and to bed. Tomorrow would be an amazing day.
Waking up at the crack of dawn was not as easy as she would believe, but with some food in her belly and class started she was as happy as she had never been before. First, it was tactics, marching preparations, and the general welfare of the troops until lunch. After that, it was weapons training and leadership. This was most of the days going forward as well as wilderness survival and healing skills. No part of their education was given to chance and only the best in their fields would teach the children of Denethor.
From this day the bond between the children of Denethor grew tighter and tighter. Many dangers they faced together and the darkening sky in the east was a sign of what was to come at them from the east.
In the year 2998 Boromir was proclaimed Captain of the white tree. Captain-General of Minas Tirith and high Warden of the white tree. Denethor was so proud of the oldest of his children. Nothing could diminish this day as celebrations went on for two full days until he set out from the white city. Ready to lead the defense of Osgiliath. Even if the dark forces of Mordor had not made a move in years it was still a prestigious position. There he learned much about leading the men and fighting in a ruined city as it was. Not even close to what it had been in the glory days of the kingdom.
The next one to get proclaimed Captain of the white city was Dinenthel. Two years after Boromir she walked to the citadel just like he had done and into the great hall and drew her sword before she kneeled before the steward and father.
Proudly she started to speak the oath.
"Here do I swear fealty and service to Gondor, and to the Lord and Steward of the realm, to speak and to be silent, to do and to let be, to come and to go, in need or plenty, in peace or war, in living or dying, from this hour henceforth, until my lord release me or death take me, or the world would end. So do I swear. Dinenthel Daughter of Denethor, steward of Gondor and the high king."
Her voice was filled with pride as she gave the oath Boromir had given just two years prior.
Then Denethor spoke.
"And this do I hear, Denethor son of Ecthelion, Lord of Gondor, Steward of the high king, and I will not forget it, nor fail to reward that which is given: Fealty with love, valour with honour, oath-breaking with vengeance"
As he was done she received back her sword. A sword Denethor himself had made for her.
"I am so proud of you my daughter. You and Boromir have made this old man proud" He said and grabbed her hard in a hug.
"Thank you, father. Thank you for giving me the chance." Dinenthel Responded.
"So am I Dinenthel. This is one of the proudest days of my life." He let her go and got ready to proclaim her orders.
"Captain Dinenthel of the white tree. Your order is to report to Captain General Boromir. Son of Denethor and be in his host. Defend Osgiliath with all cost."
"Yes my lord" She responded and walked over to Boromir, standing there proudly looking at her.
"Captain General Boromir. By order of the steward I Captain Dinenthel of the white tree report for duty.
"I Captain General Boromir of the white city. Warden of the white tree receive your order and take you under my command."
As soon as he spoke he hugged his little sister. Now a Captain before Faramir came over and the three siblings smiled and laughed together.
"You did it!" Faramir said proudly and Boromir added, "We did not doubt you a second Sister".
Dinenthel smiled and looked at them both. "I know you two doubted me much the days after Herhold took me in and convinced father to let me be trained and yet here I stand." The brothers laughed and ale was provided as well as food. Eating and song filled the halls of Denethor.
One of the last times of merriment in the halls of the steward.
The feast and celebrations went on for two days as with Boromir and on the morning of the third, they were getting ready to set out from the city. Armored up, sword at her hip and cloak on her back she looked at herself in a mirror. "Here I am," she said to herself. "A captain of Gondor" She looked over her room and all the things that she left behind. She only took her spare clothing and other necessary things. Along with the neckless she was given by her mother on her deathbed. That would never leave her neck.
With that, she left her room and walked into the main hall and Denethor stood there reaching for her and hugging her. "Do me proud as you already have my dear daughter. Look after yourself and Boromir you hear? I cannot lose both of you." She smiled and a tear came from her eye. This was the old father she remembered. She just hoped he would stay this way more than his dark self as of late. "I will father and he will look out for me. You know that". He nodded and smiled. "I do, but it has to be said or I would not stop thinking of it". Smiling at her father's comment. "Look after Faramir. I know you two do not see eye to eye. But he is your son and our brother. We love him dearly and so should you." Denethor was clearly displeased with the comment. "He is a wizard's pupil now and if not for him your mother would be here."
Dinenthel looked at her father with sadness as she tried to speak, but Denethor stopped her "Boromir is waiting for you. I will see you on your return Daughter." He hugged her again and kissed her cheeks. "Yes My Lord" was all she could say as she knew anything else would be a waste.
Leaving the hall and the seventh level of the city she came to the horses and Boromir and Faramir. Throwing the saddlebags over her horse she turned to Faramir and hugged him like she never had before. "Do not hate him. He has changed I know. But he loves you too. No matter what he says." Faramir hugged her back firmly too "I know sister. But it is so hard to believe it. He has changed so much towards me than he has of you two."
There was no secret in it and now it would be just him and Denethor left. But she had her orders and so did Boromir. All they could hope for was Faramir coming of age too and being given the rank of Captain. With it, she mounted her horse, Estel. As in such dark times all she could have was hope for a better future.
"Are you ready sister?" Boromir said as they sat on their horses while the men got ready behind them. "I am my Captain" Dinenthel responded.
Faramir stood there now alone. Not like last time when Dinenthel would remain with him. He was sad and felt an emptiness he had not felt before. Their banners flew in the wind as a gust came from the south and the horn of the city filled the air with sound.
"One-day little brother, you will come with us," Dinenthel said smiling and grabbing Faramir's arm, shaking it one last time. She rode off as Boromir did the same and she looked back and waved at him as well. The world was ahead and she still had much to learn. With Boromir at her side, they were a force to be reckoned with.