Answer: 5000 Books of Covenant.
Some extra relevant information:
Upgrading your castle in Rise of Kingdoms is a crucial step in advancing your empire and unlocking new features and benefits. Castle upgrades require a variety of resources and items, including books. However, the exact number of books needed to upgrade a castle from level 24 to 25 may vary.
To upgrade your castle from level 24 to 25, you will need a significant number of books, specifically the “Blueprint: Sanctuary” item. This item is required to increase your castle level beyond 24. The exact number of books needed for this specific upgrade can range anywhere from 50 to 100, depending on various in-game factors and events.
Gaining books for castle upgrades is not a straightforward process. You can obtain them through various means such as participating in events, completing certain quests or tasks, and opening special chests or rewards. It is important to keep an eye out for in-game opportunities to acquire these valuable items.
Additionally, joining an active alliance can be beneficial as it may provide you with access to alliance technologies that can reduce the number of books required for castle upgrades. Collaborating with alliance members and participating in events can help you earn books more efficiently.
Ultimately, the number of books needed to upgrade your castle from level 24 to 25 is subject to game updates, events, and individual gameplay progression. It is always advisable to stay informed about the latest updates and events within Rise of Kingdoms to maximize your chances of acquiring the required resources.