The mission where you're introduced to a lot of things and where you get a chance to apply the skills you got in the training mission. Infamous "taffer" and "bear pits" were born here. As well as Lord Bafford and his scepter (I'm sure it will return in some FMs later). While solid gameplay-wise with ever changing, slightly boxy environments, it's a great glimpse into the City, it's lore, architecture, population, relationships. It doesn't overpower your with walls of text and cutscenes, just throws your ways enough to make you intrigued and immersed. Starry night, grim alleys made of stone and rust, humming street lights, grumbling guards, twisty and damp sewers, the fortress-like manor, the scepter... All of that is just extremely iconic for me.