: While a melded permanent is on the battlefield, it has only the characteristics of its combined back face. The same is true while it’s on the battlefield with its front face up. : While a meld card is in any zone other than the battlefield, it has only the characteristics of its front face. If an effect instructs a player to meld cards that can’t be melded, those cards remain in exile. Tokens, cards that aren’t meld cards, or meld cards that don’t form a meld pair can’t be melded. : Only two cards belonging to the same meld pair can be melded. Counters, Auras, Equipment, and other effects that affected those two cards don’t affect the melded permanent. : When two cards are exiled and melded, they each leave the battlefield, then return together as one new object with no relation to either of the objects that left the battlefield. If you control more than one object with one of those names, you select one object with that name to exile. : One card in each pair of meld cards has an ability that instructs you to exile the two cards and meld them. If the cards are put on the top or bottom of your library, you choose their relative order. As it leaves the battlefield, both of those cards are turned face up again. If the melded creature dies, both cards are put into your graveyard. : When a pair of cards are melded, the result is a single creature that’s represented by two cards. The Mightstone and Weakstone // Urza, Planeswalker rulings:

Melded urza