Whenever a creature an opponent controls attacks one of your opponents,
doubleDoubling a creature’s power and/or toughness creates a continuous effect. This effect modifies that creature’s power and/or toughness but doesn’t set those characteristics to a specific value. See rule 613.4c.
To double a creature’s power, that creature gets +X/+0, where X is that creature’s power as the spell or ability that doubles its power resolves. Similarly, an effect that doubles a creature’s toughness gives it +0/+X, where X is that creature’s toughness. Doubling a creature’s power and toughness gives it +X/+Y, where X is its power and Y is its toughness.
If a creature’s power is less than 0 when it’s doubled, doubling that creature’s power instead means that the creature gets -X/-0, where X is the difference between 0 and its power. Similarly, if its toughness is less than 0 when doubled, it gets -0/-X. If one characteristic’s value is negative but the other isn’t when both are doubled, it gets -X/+Y or +X/-Y, as appropriate.
To double a player’s life total, the player gains or loses an amount of life such that their new life total is twice its current value.
To double the number of a kind of counters on a player or permanent, give that player or permanent as many of those counters as that player or permanent already has.
To double the amount of a type of mana in a player’s mana pool, that player adds an amount of mana of that type equal to the amount they already have.
To double an amount of damage a source would deal, that source instead deals twice that much damage. This is a replacement effect. (CR 701.10) its power until end of turn.
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Monstrosity“Monstrosity N” means “If this permanent isn’t monstrous, put N +1/+1 counters on it and it becomes monstrous.”
Monstrous is a designation that has no rules meaning other than to act as a marker that the monstrosity action and other spells and abilities can identify. Only permanents can be or become monstrous. Once a permanent becomes monstrous, it stays monstrous until it leaves the battlefield. Monstrous is neither an ability nor part of the permanent’s copiable values.
If a permanent’s ability instructs a player to “monstrosity X,” other abilities of that permanent may also refer to X. The value of X in those abilities is equal to the value of X as that permanent became monstrous. (CR 701.37) X. (If this creature isn't
monstrousA designation a permanent gains from monstrosity until it leaves the battlefield. (CR 701.37), put X +1/+1
countersTo counter a spell or ability is to cancel it: remove it from the stack without resolving it. A counter on an object or player is instead a marker that changes characteristics or interacts with rules or abilities; for example, a +1/+1 counter modifies a creature’s power and toughness. (CR 701.6; 122.1) on it and it becomes
monstrousA designation a permanent gains from monstrosity until it leaves the battlefield. (CR 701.37).)
When this creature becomes
monstrousA designation a permanent gains from monstrosity until it leaves the battlefield. (CR 701.37),
goadCertain spells and abilities can goad a creature. Until the next turn of the controller of that spell or ability, that creature is goaded.
Goaded is a designation a permanent can have. A goaded creature attacks each combat if able and attacks a player other than the controller of the permanent, spell, or ability that caused it to be goaded if able. Goaded is neither an ability nor part of the permanent’s copiable values.
A creature can be goaded by multiple players. Doing so creates additional combat requirements.
Once a player has goaded a creature, the same player goading it again has no effect. Doing so doesn’t create additional combat requirements. (CR 701.15) up to X target creatures your opponents control.