Fire Ships are a class of ships available from the Classical Age to the Enlightenment Age. They explode on contact with enemy ships, dealing significant damage to enemy ships in the immediate vicinity - as well as any friendly ships unlucky enough to be in range of the explosion. Fire ships are highly effective against Heavy Ships and Bombardment Ships, but are countered by Light Ships.
Fire Ships' production cost increases progressively with every Dock/Anchorage unit on the field or currently in production. The default increase is of 1 Wealth for the second unit created, increasing further with every new unit until the cost cap is reached, which for military units is +125% of their original base value.