Just to reiterate- yup they can be played as long as the card they represent is legal. So if it's counter-part is from Fellowship, it cannot be used. (Even though it's a promo.. there was much confusi...
I think it was in the last CRD that Sam's ring-snatching only works with Frodo as the Ring-bearer. And the old 0-cost Frodos cannot be used as a regular companion. Only Frodo, Frenzied Fighter from Bl...