Both worlds were focusing on fighting their own war, that gave Dooku and Galadriel the best opportunity to make their plan. Nobody else knew about the elf's dark trial, not even Elrond.
Dooku spent a lot of effort to turn Galadriel to the Dark Side, to let her accept his philosophy, and make the plan to confort Darth Sidious.
As for how to train her to master the Dark Side of the force, he didn't plan about it.
As a Noldor elf, she was stronger than human, but let her learn the lightsaber skills was not easy task, especially time was short.
Dooku was one of the best swordsmen in his era. He once taught General Grievous, but let Galadriel wield a lightsaber and fight the droids? He didn't want to think about such a scenario.
The fight with her showed she needed more quick skills to compensate her weakness, but at least for now, he must let her leave some weakness so he could control her.
Turning such a woman was a great victory to him, but the cunning Sith Lord knew he could not lower his guard. Betrayal was too often among the Sith. Although she couldn't be called even as a Dark Jedi for now.
Dooku decided to teach her some healing and telekinesis skills for now, save the offensive skills such as the lightning. She would not be able to master those until she had deeper understanding of hatred and anger.
Far away in another galaxy, Palpatine, the Supreme Chancellor of the Republic carefully checked his office and made sure no one was near.
"I know you're in there, old fool! Answer me!" Palpatine bitterly yelled.
But the entire office didn't have anyone else other than him, so no doubt nobody answered.
"You promised to teach me achieve eternal life but never did so. I could not let you, this old lier share power with me as co-chancellor, never."
Palpatine had never been so angry in front of people, his handsome face even twisted.
"Old fool, letting you stay behind the stage was annoying enough, how dare you ask for position like co-chancellor when you are no longer needed? "
Palpatine was like accusing an old parasite. But he completely ignored it was Plagueis' plan that made his the chancellor.
"I will become the most powerful Sith in the history and rule the most powerful Empire ever existed. However, I have to admit that old fool, nobody could compete with your knowledge of the mid-chorlian manipulation. Share your knowledge and help me achieve immortality, this is your last chance."
Still no reply in this office, this silence made Palpatine even more furious.
However, he found another way now.
The unknown new world had immortal races, their magic perhaps might help him achieve eternal life.
He went to the secret meeting place, The Mandalorians brought their master the elf lord Celeborn.
Sidious got no patience to corrupt this elf, he looked too weak and clearly wasn't worthy for him to do it.
"We will not die, our soul will return to Mandos and come back to the living world. Don't even waste time, nothing will break me."Celeborn was full of confidence, didn't know who was he dealing with.
Sidious'face under the black hood showed no expression, but his gloomy voice slowly started a tale: "Three thousand six hundred years ago, the Sith Empire once ruled half the galaxy, among those Sith Lords, there was one called Darth Nox. "
"She was a Twi'lek slave from the beginning, but then learned a mysterious skill called Force Walk. By using this skill, she bound powerful Sith Lords and Dark Jedi's ghost into her body, use them to empower herself. She defeated her rival, the powerful Darth Thanaton and thus earned a seat in the Dark Council, the ruling body of the empire. Many years ago, I was fortunate to find her Holocron, learned this skill and improved it. I can use it to control spirits to work for me without bind them into my body. "
After he finished the tale, he felt fear from this elf for the first time. Fear was the ally of the Sith. After he clear the elf's ignorance from his mind, the elf's soul could not hide anything from him.
"Get ready to let your puny soul bath the power of the Dark Side…"