According to an employee of the studio, the Toreador and Lasombra clans were not included in the developers' plans.
According to The Chinese Room, which is currently developing Vampire: The Masquerade - Bloodlines 2, the addition of the Toreador and Lasombra clans was not part of the studio's original plans, but fans really wanted to see them in the game. It was the persistence of fans that forced the developers to add them to the project upon release in the form of paid add-ons.
The studio had to do additional work after another postponement of the game, adding clans to Bloodlines 2, which, according to fans, are of certain importance to the plot and the Vampire: The Masquerade universe.
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Image author: The Chinese Room. Image source: Vampire: The Masquerade - Bloodlines 2