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City of Traitors provides two colorless mana from a single land, helping decks cast artifacts and other generic-cost spells ahead of schedule. Its drawback triggers when you play another land, forcing you to sacrifice the City. This makes it a tempo-focused mana source: the early burst can be valuable, but you need a plan for continuing development after the next land drop.
Artifact decks can use the two mana toward a turn-one mana rock or an early engine, then use those permanents to soften the loss of the land later. Expensive colorless threats also appreciate the acceleration. A deck full of colored requirements may gain less than expected, because the City cannot directly pay a required colored mana symbol.
The trigger cares about playing another land. A land put onto the battlefield by a spell or ability is a different action and does not trigger that sacrifice instruction. When you do play another land, you can normally tap the City for mana in response to its trigger, using its output one last time before the sacrifice resolves.
Consider your opening sequence rather than treating it as a land you must always play first. Delaying the City until after ordinary colored lands may give you a stronger burst on the turn that matters. It belongs in decks willing to trade some long-term land stability for immediate acceleration, with enough artifact mana, recursion, or low-cost threats to keep functioning after it leaves.
