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Quick Answer
Castle 25 is an important gate on the road to Academy 25 and T5, not a requirement to make every building level 25 before upgrading City Hall. Keep the Castle book project running alongside the rest of your account so it does not become the last expensive surprise.
Books of Covenant are the distinctive bottleneck. Count the books still required from your current level, then compare realistic fort income with the gem cost of the remaining shortfall.
What the Castle Is For
The Castle increases rally capacity as it develops and becomes part of the late Academy dependency chain. Its upgrades require ordinary resources plus Books of Covenant. Fort rewards are a source of books; gems provide an alternative acquisition route where offered. The Castle reference includes the level tables and acquisition options.
Do not confuse your ordinary march capacity with rally capacity. The Castle's rally function does not mean upgrading it immediately increases every gathering or field march by the same amount.
Calculate From Your Current Level
| Input | Where it comes from |
|---|---|
| Books for the remaining upgrades | Current Castle requirements and the levels still ahead |
| Books already in inventory | Your bag, including any relevant unclaimed rewards |
| Average books per completed fort | A sample of your own eligible rewards |
| Forts you can complete per week | Your actual alliance activity and AP budget |
| Gem price for the remaining books | The current purchase interface |
Use remaining books ÷ expected books per week for a time estimate. Books per rally multiplied by rallies per week gives books per week, not months to completion.
A Worked Example
Suppose you need 1,200 more books and your recent activity averages 120 books a week. At that pace the shortfall represents about ten weeks. If you already hold 300 of those books, the outstanding 900 represents about seven and a half weeks. These are illustrative inputs, not guaranteed fort drops.
Now compare the missing books with the next deadline. If Academy research is still months away, paying gems to finish Castle immediately may not accelerate T5 at all. If books are the final blocker and the research bank is ready, a targeted purchase has a different value.
Forts Without Guessing the Yield
Join an active alliance and follow its fort instructions. Use a suitable peacekeeping/fort pair when leading; when joining, send the requested troop amount and type rather than overfilling a rally unnecessarily.
Track completed rewards over several sessions. A single fortunate chest is not a planning average. Include AP availability and whether enough suitable forts exist at the times you play.
Castle, City Hall and T5
Use the City Hall guide for City Hall's actual prerequisite chain. Use the T5 guide for the Academy/research project. They are connected progression systems, but their direct requirements are not identical.
Before spending, write down the next blocker after Castle. Resources, other buildings, research prerequisites and time can still prevent the troop unlock. Buying books should move the actual project forward, not merely remove the most visible red requirement.
Should every player buy books during More Than Gems?
No. If you already intend to buy books, a qualifying gem-spend event can improve the timing. That does not make an unnecessary purchase sensible. Compare the next VIP milestone and other planned uses first.
Sources and Review
Source review: 9 September 2026. Game mechanics are drawn from the references below; spending priorities and play examples are editorial recommendations. This is source-reviewed guidance, not a claim of independent in-game testing.