MTG Treachery

Activated abilities contain a colon. They’re written in the form "[Cost]: [Effect]." Some keyword abilities, such as equip and crew, are activated abilities and will have colons in their reminder texts.
Triggered abilities use the word "when," "whenever," or "at." They’re often written as "[Trigger condition], [effect]." Some keyword abilities, such as prowess and fabricate, are triggered abilities and will have "when," "whenever," or "at" in their reminder text.
The Twin Princess’ ability targets an activated or triggered ability that was activated or has triggered and is on the stack. It creates another instance of that ability on the stack. It doesn’t cause any object to gain an ability.
The source of the copy is the same as the source of the original ability.
If the activated or triggered ability is modal (that is, if it says, "Choose one —" or similar), the mode is copied and can’t be changed.

If the activated or triggered ability divides damage or distributes counters among a number of targets (for example, the ability of Bogardan Hellkite), the division and number of targets can’t be changed. If you choose new targets, you must choose the same number of targets.
Any choices made when the activated or triggered ability resolves won’t have been made yet when it’s copied. Any such choices will be made separately when the copy resolves. If the activated or triggered ability asks you to pay a cost (such as that of Frenzied Goblin), you pay that cost for the copy.
If a triggered ability is linked to a second ability, copies of that triggered ability are also linked to that second ability. If the second ability refers to "the exiled card," it refers to all cards exiled by the triggered ability and the copy. For example, if Oblivion Ring’s enters-the-battlefield ability is copied and two permanents are exiled, they both return when Oblivion Ring leaves the battlefield.
In some cases involving linked abilities, an ability requires information about "the exiled card." When this happens, the ability gets multiple answers. If these answers are being used to determine the value of a variable, the sum is used. For example, if Elite Arcanist’s enters-the-battlefield ability is copied, two cards are exiled. The value of X in the activation cost of Elite Arcanist’s other ability is the sum of the two cards’ converted mana costs. As the ability resolves, you create copies of both cards and can cast none, one, or both of the copies in any order.
A mana ability is an ability that (1) isn’t a loyalty ability, (2) doesn’t target, and (3) could put mana into a player’s mana pool when it resolves.

The Twin Princesses

TOOLS

NOTES AND RULES INFORMATION FOR THE TWIN PRINCESSES