Magic: The Gathering Comprehensive Rules Changes - Time Spiral to Planar Chaos

Old rule (Time Spiral)	New rule (Planar Chaos)
104.2. [Click to view all changes.]
104.2. If a creature's power or toughness, a mana cost, a player's life total, or an amount of damage would be less than 0, it's treated as 0 for all purposes except changing that total. If anything needs to use a number that can't be determined, it uses 0 instead. Example: If a 3/3 creature gets -5/-0, it deals 0 damage in combat. But to raise its power back to 1, you'd have to give it +3/+0 (3 minus 5 plus 3 is 1). Example: If you control no permanents, the "highest converted mana cost among permanents you control" can't be determined, so 0 is used instead.	104.2. If a numerical value (such as a creature's power, toughness, or total power and toughness; a mana cost; a player's life total; or an amount of damage) would be less than 0, it's treated as 0 for all purposes except changing that total, if applicable. If anything needs to use a number that can't be determined, it uses 0 instead. Example: If a 3/3 creature gets -5/-0, it deals 0 damage in combat. But to raise its power back to 1, you'd have to give it +3/+0 (3 minus 5 plus 3 is 1). Example: If you control no permanents, the "highest converted mana cost among permanents you control" can't be determined, so 0 is used instead.

Old rule (Time Spiral)

New rule (Planar Chaos)

104.2.

If a creature's power or toughness, a mana cost, a player's life total, or an amount of damage would be less than 0, it's treated as 0 for all purposes except changing that total. If anything needs to use a number that can't be determined, it uses 0 instead.

Example: If a 3/3 creature gets -5/-0, it deals 0 damage in combat. But to raise its power back to 1, you'd have to give it +3/+0 (3 minus 5 plus 3 is 1).

Example: If you control no permanents, the "highest converted mana cost among permanents you control" can't be determined, so 0 is used instead.

104.2.

If a numerical value (such as a creature's power, toughness, or total power and toughness; a mana cost; a player's life total; or an amount of damage) would be less than 0, it's treated as 0 for all purposes except changing that total, if applicable. If anything needs to use a number that can't be determined, it uses 0 instead.

Example: If a 3/3 creature gets -5/-0, it deals 0 damage in combat. But to raise its power back to 1, you'd have to give it +3/+0 (3 minus 5 plus 3 is 1).

Example: If you control no permanents, the "highest converted mana cost among permanents you control" can't be determined, so 0 is used instead.