As the enters-the-battlefield ability resolves, first the player whose turn it is chooses which two creatures they are going to sacrifice, then each other player in turn order does the same
At the end of the exchange, you will have a Tarmogoyf and a mystery card
Because face-down creatures don't have a name, they can't have the same name as any other creature, even another face-down creature
You can play a single copy of Mental Misstep in Vintage, or in Highlander formats (including Commander!), but otherwise, youll have to read about this menace in the history books
However, the standard poker card size has 11-12 pt or 300-310 GSM card thickness to ensure high quality, durability, and ultimately the cards performance
It gives the card a textured, jagged feel unlike anything you normally see