3 flying cards and some DEC. That was my reward for completing the quest and trying to stick to Silver I. It was not easy, let me assure you. I had the Fire Quest which I am not very good at. No real good Fire cards except for the starter pack cards.
Once I had completed my quest, I was actually in Silver II and so I had a decision to make - try and promote to Silver I and then claim the prize or claim the prize straightaway.
I decided to use my Alric and try to fight for promotion. As the rewards chests in the beginning show, I was indeed able to get to Silver I and then I claimed the prize.
What's interesting is that the additional reward chest of 5 DEC more than pays for my Alric rental. So it is a net positive.