Buildings Appendix

BuildingRevenueDefenceUpgrade Cost
tower125%25 gold
keep250%25 gold
castle375%25 gold
citadel4100%25 gold

Buildings provide some protection against fire-based spells. Any garrison or leader in a province with a building has any fire damage divided by (1 + building level)

i.e. A tower will reduce fire damage by 1/2. A citadel will reduce fire damage to 1/5.