It's the same 200-odd cards that everyone else can access and, more importantly, only one or two of the rare ones are required for you to build a highly competitive deck around - after less than a week of checking in daily, I had enough for at least one, and probably with a bit of targeted play two or three, of the main competitive decks already
Then, if you have 2 or fewer security cards, place this card at the bottom of your security stack
Crustle EX and Vaporeon EX two cards ruined by heavy retreat costs
As long as one of the cards revealed is either a Digimon card with [Unidentified] in its type or an [Arata Sanada] card, you can add it to your hand
It's expected to run into a starter this early in the list, and as you might predict, it won't be the last time