Oracle

Legendary Planeswalker - Vivien 

You may look at the top card of your library any time.
You may cast creature spells from the top of your library.
+1: Create a 3/3 green Beast creature token. Put your choice of a vigilance counter, a reach counter, or a trample counter on it.
-2: When you cast your next creature spell this turn, search your library for a creature card with lesser converted mana cost, put it onto the battlefield, then shuffle your library.

Tournooi-info

Legal in: Vintage, Legacy, Modern, Standard, Commander

Officiele rulings

4/17/2020
Vivien lets you look at the top card of your library whenever you want (with one restriction; see below), even if you don’t have priority. This action doesn’t use the stack. Knowing what that card is becomes part of the information you have access to, just like you can look at the cards in your hand.

4/17/2020
If the top card of your library changes while you’re casting a spell, playing a land, or activating an ability, you can’t look at the new top card until you finish doing so. This means that if you cast the top card of your library, you can’t look at the next one until you’re done paying for that spell.

4/17/2020
Normally, Vivien allows you to cast the top card of your library if it’s a creature card, it’s your main phase, and the stack is empty. If that creature card has flash, you’ll be able to cast it any time you could cast an instant, even on an opponent’s turn.

4/17/2020
You’ll still pay all costs for that spell, including additional costs. You may also pay alternative costs such as mutate costs.

4/17/2020
The top card of your library isn’t in your hand, so you can’t cycle it, discard it, or activate any of its activated abilities.

4/17/2020
After activating Vivien’s last loyalty ability, the delayed triggered ability it creates will put a creature card onto the battlefield before the creature spell that caused the ability to trigger resolves.

4/17/2020
For spells with X in their mana costs, use the value chosen for X to determine the spell’s converted mana cost.

4/17/2020
If a card in a player’s library has X in its mana cost, X is considered to be 0.

4/17/2020
If you cast a mutating creature spell, you must choose a target for it before the triggered ability from Vivien’s last ability puts a creature onto the battlefield. The creature you find can’t be the target of the mutating creature spell.

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