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
When a monster effect is activated, while you control a Level 10 or higher DARK Dragon Synchro Monster: You can banish this card from your GY
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While I have never played against a Tergrid, God of Fright in my entire Magic career, I constantly hear how hated this card is
Existing PTCGO players will be able to transfer over the majority of their cards to the new game using their log-ins
If you meet both of those pre-requisites one of your opponents will die on the spot