I don't understand the feelings of the weak. The law of the world is survival of the fittest. It's how the weak are weeded out. It just means those people that died were too weak. It's only natural for the weak to perish.
Esdeath after drinking the blood of the Demon's Extract.
Some years later, Esdeath joined the Empire's Military, rising quickly through the ranks before she caught the attention of Prime Minister Honest and was allowed to choose an Imperial Arm for her use. After she chose the Imperial Arm known as the Demon's Extract, her perverted mind counteracting induced madness, she learned of the arrest of General Liver and released him to serve as one of her Three Beast bodyguards. Some time later, she was ordered to go with the Empire to set an example for what happens to a tribe that rebels against the Empire. Using her mastery over ice, she froze a river that cut her army off and created a bridge. After using the makeshift ice bridge to cross the river, she defeated the Ban Tribe and captured the leaders of the village.

After everything was finished, she sent the army to "violate [the] city until they were satisfied," which resulted in mass pillaging, beatings, and the murder of hundreds of innocents—as well as the burning of the entire village. She forced the leaders of the tribe to watch and kept them alive to encourage future insubordination to the Empire, so she could be sent elsewhere to fight and kill more people. The anime version notably changed the order of these events—she ordered the massacre after the ice was frozen, and simply captured the leaders at the end rather than having them watch.

421px-Esdeath lover must be
What a man needs to become Esdeath's lover.
Esdeath's recent mission was the subdue the Northern tribes that united under their prince Numa Seika. In the end, she buried over 400,000 people alive while shattering Numa's spirit and turning himself into a submissive slave before killing him with one kick out disappointed with the "hero" being weak. Upon her return to the Capitol, she declines Honest's offer of higher nobility for the request to find love, much to the chagrin of everyone in the room. She provided a short list of qualifications with the few men she knew, but it was very specific to the Emperor and the Prime Minister.

Jaegers Members
The Jaegers
At Honest's request, Esdeath sends her Three Beast bodyguards to attract Night Raid while removing the last of Honest's political rivals. When her bodyguards fell, paying her respects while dismissing their deaths as proof of their weakness, Esdeath decided to create an elite counter-assassin group comprising of her own and other Imperial Arms users. Their mission was primarily to hunt Night Raid, Esdeath named her group the "Jaegers."
Esdeath and Tatsumi fight against the Gigantic Beasts.
Sometime after Dr. Stylish's death, dealing with escaped Danger Beasts-hybrids that he created, Esdeath finds herself seeing Tatsumi on Mt. Fake before the two of them are transported by the mastermind being the hybrids' attack to an unidentified island in the Southeast. On the island, they encounter Stylish's Colossal Danger Beast hybrids. Once they dispatch the threat, the two explore the island before Esdeath eventually reveals her past with Tatsumi realizing she beyond any of redemption. When Syura's Imperial Arm reactivates, Esdeath and Tatsumi return to the mainland before the latter uses his Imperial Arm to evade her.

Later, Esdeath received a report of Night Raid sighted in the outskirts of the Empire. Along with the Jaegers, Esdeath headed toward them in expectation of finding Tatsumi. But she learned too late that was a setup that cost the life of her subordinate Bols. Following that, Esdeath is given orders to protect Bolic, an Imperial spy within the ranks of the religious order known as the Path of Peace. When Night Raid makes their move as expected, Esdeath reveals the Trump Card she created to keep Tatsumi from running away from her: Mahapadma. Once Bolick was assassinated, Susanoo sacrificed himself to enable the others to escape. Esdeath kills the humanoid Imperial Arm by destroying his core, promising to recognize him as a warrior instead of a tool.

After subduing the tribes of the Western Nation, Esdeath returns to learn that the newly formed Wild Hunt squad led by Honest's son Syura had killed her subordinate Run who Kurome revived as a corpse. Esdeath retaliates by extorting Honest to order the immediate disbanding of Wild Hunt after obtaining evidence that Syura was the person behind the release of Stylish's experiments.

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Esdeath concluding that Tatsumi will be killed by her own hands.