The dot left to the name indicates, that you can have only 1 "Darth Vader" in your fleet.
Rule
Star Wars Armada includes many famous characters and ships from the Star Wars universe. Each of these famous figures is represented by a card with a unique name, which is identified by a bullet (•) to the left of the name. A player cannot field two or more cards that share the same unique name.
As stated by the developers in Rebellion in the Rim video, squadron names printed in italicised letters like Millenium Falcon also count as unique.
Cards with Unique
- All cards with the • Unique trait.
- Squadron Cards with the • Unique trait.
- Cards that share a unique name with at least 1 other card