If a creature’s power is less than 0 when it’s tripled, tripling that creature’s power instead means that the creature gets -X/-0, where X is twice the difference between 0 and its power. Similarly, if its toughness is less than 0 when tripled, it gets -0/-X. If one characteristic’s value is negative but the other isn’t when both are tripled, it gets -X/+Y or +X/-Y, as appropriate.
April 27, 2018 · Dominaria
rule 701.11c not present in this release
September 30, 2016 · Kaladesh
If a creature fights itself, it deals damage equal to its power to itself twice.
May 1, 2014 · Journey into Nyx
Some effects instruct a player to “play” with a certain aspect of the game changed, such as “Play with the top card of your library revealed.” “Play” in this sense means to play the Magic game.
September 30, 2011 · Innistrad
Some effects instruct a player to "play" with a certain aspect of the game changed, such as "Play with the top card of your library revealed." "Play" in this sense means to play the _Magic_ game.
June 17, 2011 · Commander 2011
Neither activating an ability that creates a regeneration shield nor casting a spell that
April 1, 2011 · Duel Decks: Knights vs. Dragons
Neither activating an ability that creates a regeneration shield nor casting a spell that creates a regeneration shield is the same as regenerating a permanent. Effects that say that a permanent can't be regenerated don't prevent such abilities from being activated or such spells from being cast; rather, they prevent regeneration shields from having any effect.
February 4, 2011 · Mirrodin Besieged
Neither activating an ability that creates a regeneration shield nor casting a spell that creates a regeneration shield is the same as regenerating a permanent. Effects that say that a permanent can’t be regenerated don’t prevent such abilities from being activated or such spells from being cast; rather, they prevent regeneration shields from having any effect.
October 1, 2010 · Scars of Mirrodin
Neither activating an ability that creates a regeneration shield nor casting a spell that
February 1, 2010 · Worldwake
Neither activating an ability that creates a regeneration shield nor casting a spell that creates a regeneration shield is the same as regenerating a permanent. Effects that say that a permanent can't be regenerated don't prevent such abilities from being activated or such spells from being cast; rather, they prevent regeneration shields from having any effect.