I believe very much that going on to list combos after ~200 different cards is a bit silly, but this one surprised me so it's more something to look out for for all you Dark Ages newbies out there. I'm a big DA novice myself and because I don't have the cards memorized it's even harder to spot easy combos.
Okay, we all know that we can Expand Peddlers into Colonies. So far, so good.
The reason I'm creating this topic especially for Graverobber is that it's easy to misinterpret the card, again mostly if you are new to DA. Why is this?
It's simple: Graverobber specifies that you must trash an Action card to gain a card costing up to $3 more. So you must use an Action card on the way in, but you can gain ANY card type on the way out. It's easy to think you can only transform Action cards into other Action cards.
Now you see the interaction between Graverobber and Peddler. Gain Peddlers, Graverobber them into Colonies. You can't Graverob the Peddlers back without the use of a cost-lowering card (remember that Peddler's cost is only lowered during the buy phase).
This combo is not game warping in the sense that you can rely on it alone to make you win the game. Of course, after you've Graverobbered 4 Peddlers into Colonies there are still 4 other Colonies for your opponent or yourself. You also need some support to easily gain the Peddlers.
So I will repeat myself and say that this isn't anything earth shattering, but it caught me off guard the other day, so I might as well share it to prevent new players from making the same oversight.