I remember this has been discussed a few times, but sadly the search function is rather disapointing in the new forums.
So anyway, if you have to pay 0 gold as a cost for a effect, like with the new Targ character who steals attachments, can you trigger the effect for free, or ist it the same like with influence so that you cannot kneel 0 influence, and therefore have to kneel at least one influence/ pay one gold?
Thanks in advance!
Couple of things here:
First, when a card has a printed 0-gold cost (like Great Keep, Narrow Sea or Bolton Refugee), can you play the card for free? Of course. The card still has a gold cost, it just happens to be 0. So while you essentially get the card for free, you can only play it when you would be allowed to spend gold/play the card/meet all other play restrictions. Same thing if an effect has a 0-gold cost. You essentially get it for free (you don't need to put gold resources into triggering it), but you can still only trigger it when you meet all other timing and play restrictions.
Second, where did you get the idea that you cannot kneel/pay 0 influence? If you have an effect that requires you to kneel X influence (like Gathering of the Clans from the HoTal set) or to kneel influence equal to the printed gold cost of another card (like Daario Naharis, also from HoTal), that influence cost can be equal to 0. In that situation, it looks a lot like the gold discussion above - you essentially trigger it for free provided you can meet the rest of the play restrictions. It is perfectly legal to "kneel" 0 influence, provided that this actually pays an applicable effect cost.