General Rulings - 107

• 107.1 - The only numbers the Magic game uses are integers. [CompRules 2009/07/08]
• 107.1a - You can't choose a fractional number, deal fractional damage, gain fractional life, and so on. If a spell or ability could generate a fractional number, the spell or ability will tell you whether to round up or down. [CompRules 2009/07/08]
• 107.1b - Most of the time, the Magic game uses only positive numbers and zero. You can't choose a negative number, deal negative damage, gain negative life, and so on. However, it's possible for a game value, such as a creature's power, to be less than zero. If a calculation or comparison that would determine the result of an effect needs to use a negative value, it does so. If such a calculation yields a negative number, zero is used instead, unless that effect sets a player's life total to a specific value, sets a creature's power or toughness to a specific value, or otherwise modifies a creature's power or toughness. [CompRules 2009/07/08]
  Example: If a 3/4 creature gets -5/-0, it's a -2/4 creature. It assigns 0 damage in combat. Its total power and toughness is 2. You'd have to give it +3/+0 to raise its power to 1. [CompRules 2009/07/08]
  Example: Viridian Joiner is a 1/2 creature that says "{Tap}: Add an amount of {G} to your mana pool equal to Viridian Joiner's power." An effect gives it -2/-0, then its ability is activated. The ability adds no mana to your mana pool. [CompRules 2009/07/08]
• 107.2 - If anything needs to use a number that can't be determined, either as a result or in a calculation, it uses 0 instead. [CompRules 2009/07/08]
• 107.3 - Many objects use the letter X as a placeholder for a number that needs to be determined. Some objects have abilities that define the value of X; the rest let their controller choose the value of X. [CompRules 2009/07/08]
• 107.3a - If a spell or activated ability has a mana cost, alternative cost, additional cost, and/or activation cost with an {X}, <--X->, or X in it, and the value of X isn't defined by the text of that spell or ability, the controller of that spell or ability chooses and announces the value of X as part of casting the spell or activating the ability. (See Rule 601, "Casting Spells.") While a spell is on the stack, any X in its mana cost equals the announced value. While an activated ability is on the stack, any X in its activation cost equals the announced value. [CompRules 2009/10/01]
• 107.3b - If a player is casting a spell that has an {X} in its mana cost, the value of X isn't defined by the text of that spell, and an effect lets that player cast that spell while paying neither its mana cost nor an alternative cost that includes X, then the only legal choice for X is 0. This doesn't apply to effects that only reduce a cost, even if they reduce it to zero. See Rule 601, "Casting Spells." [CompRules 2009/07/08]
• 107.3c - If a spell or activated ability has an {X}, <--X->, or X in its cost and/or its text, and the value of X is defined by the text of that spell or ability, then that's the value of X while that spell or ability is on the stack. The controller of that spell or ability doesn't get to choose the value. Note that the value of X may change while that spell or ability is on the stack. [CompRules 2009/10/01]
• 107.3d - If a cost associated with a special action, such as a suspend cost or a morph cost, has an {X} or an X in it, the value of X is chosen by the player taking the special action as he or she pays that cost. [CompRules 2009/07/08]
• 107.3e - Sometimes X appears in the text of a spell or ability but not in a mana cost, alternative cost, additional cost, or activation cost. If the value of X isn't defined, the controller of the spell or ability chooses the value of X at the appropriate time (either as it's put on the stack or as it resolves). [CompRules 2009/07/08]
• 107.3f - If a card in any zone other than the stack has an {X} in its mana cost, the value of {X} is treated as 0, even if the value of X is defined somewhere within its text. [CompRules 2009/07/08]
• 107.3g - All instances of X on an object have the same value at any given time. [CompRules 2009/07/08]
• 107.3h - Some objects use the letter Y in addition to the letter X. Y follows the same rules as X. [CompRules 2009/07/08]
• 107.4 - The mana symbols are {W}, {U}, {B}, {R}, {G}, and {X}; the numerals {0}, {1}, {2}, {3}, {4}, and so on; the hybrid symbols {W/U}, {W/B}, {U/B}, {U/R}, {B/R}, {B/G}, {R/G}, {R/W}, {G/W}, and {G/U}; the monocolored hybrid symbols {2/W}, {2/U}, {2/B}, {2/R}, and {2/G}; and the snow symbol {S}. [CompRules 2009/07/08]
• 107.4a - There are five primary colored mana symbols: {W} is white, {U} blue, {B} black, {R} red, and {G} green. These symbols are used to represent colored mana, and also to represent colored mana in costs. Colored mana in costs can be paid only with the appropriate color of mana. See Rule 202, "Mana Cost and Color." [CompRules 2009/07/08]
• 107.4b - Numeral symbols (such as {1}) and variable symbols (such as {X}) represent generic mana in costs. Generic mana in costs can be paid with any type of mana. For more information about {X}, see Rule 107.3. [CompRules 2009/07/08]
• 107.4c - Numeral symbols (such as {1}) and variable symbols (such as {X}) can also represent colorless mana if they appear in the effect of a spell or ability that reads "add <-mana symbol-> to your mana pool" or something similar. (See Rule 107.3e.) [CompRules 2009/07/08]
• 107.4d - The symbol {0} represents zero mana and is used as a placeholder for a cost that can be paid with no resources. (See Rule 116.5.) [CompRules 2009/07/08]
• 107.4e - Hybrid mana symbols are also colored mana symbols. Each one represents a cost that can be paid in one of two ways, as represented by the two halves of the symbol. A hybrid symbol such as {W/U} can be paid with either white or blue mana, and a monocolored hybrid symbol such as {2/B} can be paid with either one black mana or two mana of any type. A hybrid mana symbol is all of its component colors. [CompRules 2009/10/01]
  Example: {G/W}{G/W} can be paid by spending {G}{G}, {G}{W}, or {W}{W}. [CompRules 2009/07/08]
• 107.4f - The snow mana symbol {S} represents one generic mana in a cost. This generic mana can be paid with one mana of any type produced by a snow permanent (see Rule 204.4f). Effects that reduce the amount of generic mana you pay don't affect {S} costs. (There is no such thing as "snow mana"; "snow" is not a type of mana.) [CompRules 2009/07/08]
• 107.5 - The tap symbol is {Tap}. The tap symbol in an activation cost means "Tap this permanent." A permanent that's already tapped can't be tapped again to pay the cost. A creature's activated ability with the tap symbol in its activation cost can't be activated unless the creature has been under its controller's control continuously since his or her most recent turn began. See Rule 302.6. [CompRules 2009/07/08]
• 107.6 - The untap symbol is {Untap}. The untap symbol in an activation cost means "Untap this permanent." A permanent that's already untapped can't be untapped again to pay the cost. A creature's activated ability with the untap symbol in its activation cost can't be activated unless the creature has been under its controller's control continuously since his or her most recent turn began. See Rule 302.6. [CompRules 2009/07/08]
• 107.7 - Each activated ability of a planeswalker has an arrow-shaped loyalty symbol in its cost. Positive loyalty symbols point upward and feature a plus sign followed by a number or an X. Negative loyalty symbols point downward and feature a minus sign followed by a number or an X. <-+N-> means "Put N loyalty counters on this permanent," and <--N-> means "Remove N loyalty counters from this permanent." [CompRules 2009/07/08]
• 107.8 - A tombstone icon appears to the left of the name of many Odyssey block cards with abilities that are relevant in a player's graveyard. The purpose of the icon is to make those cards stand out when they're in a graveyard. This icon has no effect on game play. [CompRules 2009/07/08]
• 107.9 - A type icon appears in the upper left corner of each card from the Future Sight set printed with an alternate "timeshifted" frame. If the card has a single card type, this icon indicates what it is: claw marks for creature, a flame for sorcery, a lightning bolt for instant, a sunrise for enchantment, a chalice for artifact, and a pair of mountain peaks for land. If the card has multiple card types, that's indicated by a black and white cross. This icon has no effect on game play. [CompRules 2009/07/08]
• 107.10 - The planeswalker symbol is {P}. It appears on one face of the planar die used in the Planar Magic casual variant. See Rule 901, "Planar Magic." [CompRules 2009/10/01]
• 107.11 - The chaos symbol is {C}. It appears on one face of the planar die used in the Planar Magic casual variant, as well as in triggered abilities that refer to the results of rolling the planar die. See Rule 901, "Planar Magic." [CompRules 2009/10/01]