Hmm. By my current interpretation of the rules, neither Death Cart nor Border Village can be properly Summoned, the way the Event is worded.
* Gain an Action card costing up to
.
- Okay, I gain a Death Cart. That goes into my discard pile, and two Ruins get thrown on top of it.
* Set it aside.
- Set what aside? All I see in my discard pile is a Ruins. I must have lost track of something...
* If you do, then at the start of your next turn, play it.
- Play what?
EDIT: This is similar to how, with Border Village, after I gain it, I choose whether to gain the other card or to reveal Watchtower first. If I choose to gain the other card first, that goes on top of Border Village, which I've now lost track of, and can neither trash nor top-deck with Watchtower.