Lin xiao was surprised from Caelum offer since it was a golden opportunity for his children's future. He knew that the person was an expert on how easily caelum was able to heal his wounds. The power he sense may be Yuan Dan stage but his instinct as a cultivator and fighter knew that his prowess is beyond that.
It was true as despite only being at the Yuan Dan stage his prowess was already in the Profound Death only step away from Samsara stage bur Caelum refused to advances and only make sure his foundation doesn't have any flaws. Caelum overall power is hard to scale as nothing would be able to harm him beside his own training.
He gave the offer not only for Lin dong but also Qing tan which confused Lin xiao as his daughter isn't someone who trains or likes fighting. Caelum already analyzed her physique which isn't what people may think as it was powerful Yin body.
He can create a Fiend god cultivation for her or even Lin dong. Caelum could tell that she's quite adept in [Dao of Yin] while Lin dong was a [Dao of heart] because of how low his talent is but has the will reach higher stage.
"Wait Senior I understand my son but why my daughter?"
"She has special physique that is great for cultivating the profound yin. A normal yin couldn't compare to a profound yin as wisp of it is comparable to ocean of normal yin. This reason is why she may die if not nurture properly."
Caelum wasn't lying and unsure if it was the same as the canon but knew that her physique is powerful one in the ways of Yin. He knows because of the boundless knowledge in Immortal cultivation arts. The knowledge has mentions of physiques that suite for the cultivation Profound yin.
Lin dong who was busy training heard him was shocked that Qing yan had hidden physique and Lin xiao is shocked since he recalled the times the little girl experiences extreme coldness from time to time but it had grown more recently. Caelum saw Lord marten scoff thinking he was talking nonsense about profound Yin which he only ignored because his an ignorant prideful beast.
"No wonder Qing Yan experience extreme coldness. Does not mean if she doesn't cultivate then…"
"No need to worry she's not dying or anything unless you don't let me train her."
Lin xiao contemplate as in exchange of letting his daughter cultivate then she would have to fight and face the harsh reality of the world. He already let Lin dong to be his disciple but unsure of Qing Tan.
Qing Tan who heard it became scared that she may lost her life but hearing that Caelum has a solution and even make stronger then she made determined expression. She recalled being protected and decided to stand up as she doesn't want to burden her family because of her sickness and want to fight to protect them. In the canon, she was obsess with Lin dong in this timeline its not so much and only view him as brother. Not to mention, Caelum had struck her maiden heart and want to know more about him.
"Father! Qing tan will accept senior offer to become stronger and not make any of you worried!"
Lin Xiao surprised from Qing Tan sudden arrival and was even shocked seeing her determined gaze. He smiled that the girl had mature slightly and only gave his approval of the matter. Lin Xiao can't shelter her forever and needed to let Qing Tan experience the world. Caelum knowing that with his luck virtually endless able to gain Qing Tan as his first disciples along with Lin dong. They would prove useful as it let his future sect blossom into mighty dragon.
"If that's your choices then I'll support you. How about you Lin dong do you accept Seniors offer?"
Lin dong wanted to accept but was hesitant because of the Stone talisman. He doesn't want it be exposed and thought Caelum may just steal it when he found out. Caelum only smiled that the boy thought about his family even though the opportunity already showed itself. It was obvious that his afraid of exposing the treasure and bring disaster to his family.
"Hahaha I didn't expect when I decided to build my own sect would have a disciple to be hesitant. Little dong, no need to worry about secrets as I have endless secret that will never share to you and respect your privacy."
He was matured and realize that Caelum already sense about the stone talisman but remained calmed and understood he has no ill will. Lin dong decided to accept him as his master to reach his goal to show the power being bestow upon him. Caelum understood the custom that master is a second father in cultivation world and only smiled to gain 'Potential' to his path.
Qing Tan went beside Lin dong as the two was about to Kowtow but was stopped by invisible force surprising Lin dong as it was Yuan energy. Caelum used mental energy that was easily to control due to Eye of wisdom in the past which had power over telekinesis but now it is more precise and powerful.
"I dislike something kowtowing to me unless their my enemies. First thing you need to know that never bow to me or even the heaven that is what my path is. Second, many people may thing that talent and luck is the main thing that one need to become strong but theirs many more."
"What would that be, Master? (Lin dong)
"To name a few is Undying will and Hard work"
Caelum who walked to a path that transcend the strong need undying will without it then having eternal life would make crumble from how much his mind would deteriorated. The arrogant people won't ever realize that the highest is lonely places and would likely break their will. A true strong is the will to surpass not your enemy but yourself.
Lin dong only nodded even though he was slow at comprehending his words. However, Qing Tan surprisingly understood it since she personally saw the Undying will of Lin dong and her father. She had the talent to comprehend Caelum words giving her an insight in death. Caelum knew once she cultivate the [Dao of Yin] then her personality would shift into cold beauty yet still retain her old one.
"Oh Lin xiao you can listen to my teaching if you want."
"Ah are you sure, Senior?"
"I don't mind because you're the father of my disciples. Anyway, I see that you are 4th tempered body and Qing tan 2nd tempered body not bad. As for my first disciple of my unofficial sect who's name I still hadn't decided will begin by wearing this."
Caelum took out a bracelet that seem normal but once place on the children instantly felt their weight had increased by five times. He was surprise that they are able to remain standing and understood that Chinese cultivation defies logic. Qing Tan felt tired but pushed herself that instantly cause her to become tempered 4th layer surprising Lin xiao from the scenes even felt proud that the heaven had bless them of meeting Caelum.
Lin dong broke through the 5th layer shocking him but then the weight increased making it harder to move. It was simple tool that keep increasing where the user struggle enough without making them use to the weight.
"You will remove that bracelet until I told you to. Once you reach the peaked of tempered body then I'll give a reward. Now as for your true training…"
Caelum created a small pillars that meant to be jumping and training acrobatic reflexes. He saw them baffled at the things being created out of nothing but felt the Yuan energy within them. It was more easy if he used Izanagi along with Void/nothingness law but Caelum felt it wasn't necessary.
He showed what they are task to do and surprised how hard it was. Caelum let Qing Tan off because she wasn't suited for it and let Lin dong experience hell. However, the kid didn't give up and kept going while Caelum able to absorb more of 'potential'.
While he was training, Caelum thought Qing Tan on how to refined her body in proper ways and her talent was able to absorbed it without problem. She was able to comprehend everything Yin which was Death, Destruction, Darkness, coldness, etc. However, her main Dao was [Dao of Yin] which was perfect for Caelum who his understand on it. While Lin dong was in his way to have the [Dao of Heart] which best suited for his undying will.