So i was playing with some guys and i we where wondering at a few things. 1. Does open group mean any group? would i be able to bring in darth vador if i saved enough threat up? 2. How does bleed affect imperials? Thats about it for now thanks for the great answers.

Open group means any deployment card that is not Unique (so Vader, Weiss, and IG88 are not eligible choices), unless you have won the mission that rewards them as a campaign unlock, and then you can choose them as one of your open groups.

Bleed affects imperials just like heroes, with the exception that imperials cannot suffer strain, so they instead suffer damage.

References:

"Allies" RRG, Page 4.

Imperial allies are referred to as villains. They follow all of the same rules as allies, in addition to the following:

• Once gained as a reward, villains (such as “Darth Vader”) can be brought into any mission as an open group.

"Strain" RRG, Page 23

When any other figure suffers (strain), it suffers an equal amount of (damage) instead.