City of Iron: Experts and Engines brings the first expansion that deepens the Arzium universe with an even greater focus on science and engineering. The game gains a set of unique civilian and military cards for each nation—humans, Cresarians, toads, and pig‑men—that introduce new synergies and strategic combinations. Each nation now has card options that explore the "deck, bag, and pool building" mechanic, allowing players to collect research and resource sets more dynamically. In addition to the cards, the expansion introduces two types of tokens: Steambot and Kraxian Pirates. Steambot tokens can be placed on construction cards to produce extra resources, while Kraxian Pirates can be used to negate coin bonuses on resource cards, adding a layer of blocking tactics. The "open drafting" mechanic also receives attention, as cards are distributed in packs that all players have access to, making card selection more strategic. For those who already master the base game, the expansion offers extra depth in the "area majority/influence" mechanic, with new cards that change how territory control is determined. The gameplay experience remains balanced, with games lasting about 120 minutes and keeping the same learning curve. However, the expansion requires attention to translation, as the cards are published in English; it is recommended to use translation sheets or already translated versions. In short, City of Iron: Experts and Engines is an addition that increases card variety, introduces strategic tokens, and keeps the base game fun, while also offering new deck‑building and influence tactics. Players who prefer a more tactical style can combine Steambot tokens with energy research cards to accelerate resource production, while Kraxian Pirates are ideal for interrupting opponents’ coin advantages that heavily rely on resource cards. This interaction creates moments of tension and strategic decision‑making that enrich the experience.