Advanced Combat Techniques: Volume Two

Your town stops being decoration. The book pushes every villager up in health, defense, damage and swing rate at once, roughly the jump they get for free each time you clear another boss. A settlement that used to lose someone every Blood Moon starts holding its own, and during a goblin or pirate landing the residents genuinely thin the wave instead of dying in the first ten seconds.

If you have ever built a walled town and watched it fail anyway, this is the fix that costs you nothing to maintain.

It costs a Spell Tome dropped into Shimmer, which is close to free, and the effect is permanent but single use for that world. It also stacks with Advanced Combat Techniques, and the order you consume them in makes no difference, so there is no reason to hold either one back. Read both as soon as you can reach Shimmer.