Playing heroes/villains

[abc1445742535]

When you're playing a hero or villain, a bar appears at the bottom middle of the screen.  The pictures are different for different characters, for example, Luke has chevrons, Vader has shields, one has dice.  What do these mean and how are they triggered, positively or negatively?  Thanks!  

[Wsmasher]

These are the traits for heroes/villains that are activated through kills or hero damage. If you activate one circle, you will get a short description telling you what it does. For example, if luke kills about 2 stormtroopers or hit darth vader, you will get a speed boost. But other hero traits are activated differently, such as vader's trait only increasing by surrounding enemies.