You know those upgrades that completely shift the game's momentum? 'Clockwork Fortress and Cave Market Promo' is exactly that for City of Iron. We aren't talking about a full standalone game, but a duo of promotional cards that provide an extra boost to your urban construction and resource management strategies. If you're already into the steampunk vibe of Arzium, these cards are like special seasonings for your session.

First, we have the Cave Market. This card is all about pure economics: it increases your income based on the variety of goods you own. In other words, the more diverse your stock, the more coins you pocket. It's the perfect choice for players who prefer diversifying production rather than focusing on a single resource.

Then, there's the Clockwork Fortress, which tweaks your game's logistics. It allows you to rearrange the order of your citizen and military decks every time you refresh them. For those who love meticulous planning and hate the randomness of card draws, this is a dream come true, granting much tighter control over your sequence of actions.

The best part is their versatility. If you're playing the 1st edition, they fit into the 'E' buildings and are available from the start. If you've already moved to the 2nd edition, they are placed above the usual building row and stay there until purchased. Basically, they add new tactical layers and build options that can completely change the table's dynamics, making the race for city dominance even more intense.