Dagmar Ruskovitch was one of the Knights of the Solitary Sword, and positioned herself as the Baroness of Castle Houska in Central Bohemia in 1601. According to Tycho Brahe, she was described as being "as formidable as she [was] beautiful."
Dedicated to protecting the order of the universe no matter the cost, Ruskovitch and her ally Dominik learnt of the Children of Chaos, dedicated to opening up links to the Catastrophia and destroying the universe. 300 years after the Catastrophia's Herald was sealed by the creation of Castle Houska, the seal began to break down, prompting Ruskovitch and Dominik to travel to 1601 Bohemia and enlist the humans of the time to help seal it again. Positioning herself as the Baroness of the castle, Ruskovitch organised a gathering of astronomers, mathematicians, and scientists from across the world, of which Tycho Brahe was the most famous guest. He was accompanied by his then-student, Johannes Kepler, and later joined with the Thirteenth Doctor, Graham, Yaz, and Ryan to visit the gathering.
As everyone had arrived at the party, she greeted them, the Doctor introduced herself and probed her, but her questions were quickly shrugged off. She later met Kepler and Yaz, inviting Kepler to a private showing of her literary collection, where she told him that he had great potential and gave him a glowing orb that would show him new knowledge. However, this was interrupted by Brahe, Graham and Yaz, where she realised their connection to the Doctor and promised to kill her and her companions, transforming into a centaur in doing so. However, she was stopped by Kepler and agreed to spare their lives while taking him with her. She later distributed her orbs to the rest of the gatherers, which began paralysing them. With her plan in action and a twisted creature rising in the cellar, she began to control Kepler as well, but Graham and Yaz shattered the orbs.
Meeting the Doctor again, she attempted to kill her but was trapped by a falling bookcase. In doing so, she told the Doctor she had doomed the planet, as she did not summon the creature, but was actually attempting to prevent it from appearing by harnessing the astronomers' orderly minds to keep the logic web shut, led by Kepler. With the Doctor riding on her back, Ruskovitch followed the summoned Herald and shot it with an arrow, and as the Doctor attacked it with a logic orb, it was led back to the castle, where it was trapped by the logic web of the astronomers and sealed away again.
With the problem solved, Ruskovitch and Dominik opened a tunnel to take them away. The Doctor, furious that Brahe had died to enact her plans, told them that she hoped they would never meet again before they disappeared. (COMIC: Herald of Madness)