Basically the plot is about Elena taking revenge on Grand Duke Friedrich and his cronies for what they did to her in the 1st timeline. She plans to utterly crush and destroy his noble house, namely by taking advantage of an upcoming art/culture renaissance.
She plans to build herself up as independent "mysterious society lady/arts patron" L with a network of allies, followers and personal wealth and become the leading figure of said arts movement, sabotage the Friedrich's own plans to become arts leaders, and then use her authority to expose their misdeeds.