Titania, Gaea Incarnate

A player prompted to name a card may name the combined back face, and each player has the right to know that combined back face's characteristics at all times.

The mana value of a melded permanent is the sum of the mana values of its front faces. A creature that becomes a copy of a melded permanent has only the characteristics of that combined back face, and its mana value is 0.

Note that the permanent represented by the combined back faces has a color indicator.

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. Counters, Auras, Equipment, and other effects that affected those two cards don't affect the melded permanent.

In the Commander variant, a meld card's color identity is determined only by the mana costs and mana symbols in the rules text of its front face. No symbols or rules text of the permanent it melds into are considered.

If an effect moves a melded permanent to a new zone and then affects "that card," it affects both cards.

Only two cards belonging to the same meld pair can be melded. Tokens, cards that aren't meld cards, or meld cards that don't form a meld pair can't be melded. If an effect instructs a player to meld cards that can't be melded, those cards remain in exile.

While a meld card is in any zone other than the battlefield, it has only the characteristics of its front face. The same is true while it's on the battlefield with its front face up.