Oko, Lorwyn Liege // Oko, Shadowmoor Scion

To transform a permanent, turn it over so that its other face is up. Only transforming tokens and permanents represented by transforming double-faced cards can transform. (See rule 712, “Double-Faced Cards.”)

Although transforming a permanent uses the same physical action as turning a permanent face up or face down, they are different game actions. Abilities that trigger when a permanent is turned face down won’t trigger when that permanent transforms, and so on.

If a spell or ability instructs a player to transform a permanent that isn’t represented by a transforming token or a transforming double-faced card, nothing happens.

If a spell or ability instructs a player to transform a permanent, and the face that permanent would transform into is represented by an instant or sorcery card face, or is a transforming token that was created with an instant or sorcery face, nothing happens.

Some triggered abilities trigger when an object “transforms into” an object with a specified characteristic. Such an ability triggers if the object either transforms or converts (see rule 701.50) and has the specified characteristic immediately after it does so.

If an activated or triggered ability of a permanent that isn’t a delayed triggered ability of that permanent tries to transform it, the permanent does so only if it hasn’t transformed or converted since the ability was put onto the stack. If a delayed triggered ability of a permanent tries to transform that permanent, the permanent does so only if it hasn’t transformed or converted since that delayed triggered ability was created. In both cases, if the permanent has already transformed or converted, an instruction to do either is ignored.

Some spells and abilities refer to a “transformed permanent.” This phrase refers to a permanent on the battlefield with its back face up that’s also a transforming double-faced card or a transforming token. A permanent with its front face up is never considered a transformed permanent, even if it had its back face up previously.

For a player to mill a number of cards, that player puts that many cards from the top of their library into their graveyard.

A player can’t mill a number of cards greater than the number of cards in their library. If given the choice to do so, they can’t choose to take that action. If instructed to do so, they mill as many as possible. Similarly, the player can’t pay a cost that includes milling a number of cards greater than the number of cards in their library.

An effect that refers to a milled card can find that card in the zone it moved to from the library, as long as that zone is a public zone.

If an ability checks information about a single milled card but more than one card was milled, that ability refers to each of the milled cards. If that ability asks for any information about the milled card, such as a characteristic or mana value, it gets multiple answers. If these answers are used to determine the value of a variable, the sum of the answers is used. If that ability performs any actions on “the” card, it performs that action on each milled card. If that ability performs any actions on “a” card, the controller of the ability chooses which card is affected.