We just played our second game last night and got a card that mentioned a bonus to a character depending on how many cards had omen icons (or something like that).

I can't find anything that tells me what an Omen icon is.

Thanks.

It's a cross-like white sign that appears on many Threat cards.

Check for it on cards like Howling Banshee(yellow Threat -Eldar enemy), or Possessed Psyker(blue threat card-Stranger Encounter)

That was it. Thank you very much. Not sure why I couldn't find that in the instructions. but it's good to know now.