The Book of Covenant (colloquially, books) is an item which is required in order to upgrade the Castle. It is similar to the Arrow of Resistance, which is used to upgrade the Watchtower.
Description
Books can be obtained by defeating Barbarian Forts on the map, in the Shop, or purchased for 10 
Gems each when attempting to upgrade the castle with insufficient books.
| Item | Description | Gained from |
|---|---|---|
 | Can be used to upgrade the castle. |
|
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