In the core set there is no rules about Shadows, My brother bought to expansion sets that included shadows cards, and we now have some booster packs with shadows cards and shadows mechanics and we don't really know how it works. Is there an easy explanation or a web link to go to for the rules clarification of shadows cards?

You're in the wrong forum. This one is about AGOT - The Boardgame and I guess you wanted to ask this about the living card game. Go to: http://www.fantasyflightgames.com/edge_foros_temas.asp?efid=10&efcid=4 You should get an answer there.