Anno 117: Pax Romana's first expansion, Prophecies of Ash, has drawn "mostly negative" reviews on Steam, echoing wider criticism that the base game feels empty and underdeveloped compared with its predecessor, Anno 1800. However, this Polygon writer argues the DLC is unfairly maligned, as it introduces a volcanic eruption mechanic that adds welcome structure and complexity to the game's mid-game city-building loop, which previously felt like a repetitive continuation of existing systems.

The new content only activates once a player's Equites population reaches 500, after which they must complete tasks such as quarrying marble, stockpiling food and restricting goods from consumption in preparation for an eruption. When the volcano, named Occasus, finally erupts, it damages buildings, lowers fire safety, and triggers acid rain and a "volcanic winter" that slashes agricultural and aquatic output to 25% of normal levels. Afterwards, the ash enriches the soil and boosts obsidian availability, creating a cycle of hardship and recovery that the writer says is well-paced and adds engaging challenge without feeling poorly timed.