Lightmares Christmas gift to those who are currently in beta is special promo/alternative art version of the secluded constructor. This is valid until Jan 5th, and all you have to do is log in.
Remember Infinity Wars is the dTCG made by relatively small Indies company, lightmares. The game has several unique implementation compared to the other dTCG, and I believe this is a dark horse dTCG made in 2013. Currently, you can enter into the beta for free, and you can earn cards through playing it. I believe you can actually get any card in the game by playing but those are not tradable, which I think is very fair.
In any event, if you haven’t tried this game yet, there is nothing to lose. So give it a shot. If you need a invitation code, here is one (4C680).