Cankerous Thirst — ruling 1

The spell cares about what mana was spent to pay its total cost, not just what mana was spent to pay the hybrid part of its cost.

Cankerous Thirst — ruling 2

The spell checks on resolution to see if any mana of the stated colors was spent to pay its cost. If so, it doesn't matter how much mana of that color was spent.

Cankerous Thirst — ruling 3

If the spell is copied, the copy will never have had mana of the stated color paid for it, no matter what colors were spent on the original spell.

Cankerous Thirst — ruling 4

The spell cares about what mana was spent to pay its total cost, not just what mana was spent to pay the hybrid part of its cost.

Cankerous Thirst — ruling 5

When you cast the spell, you choose its targets before you pay for it.

Cankerous Thirst — ruling 6

The spell checks on resolution to see if any mana of the stated colors was spent to pay its cost. If so, it doesn't matter how much mana of that color was spent.

Cankerous Thirst — ruling 7

If the spell is copied, the copy will never have had mana of the stated color paid for it, no matter what colors were spent on the original spell.

Cankerous Thirst — ruling 8

As you cast Cankerous Thirst, you must target a creature for the first effect and you must target a creature for the second effect. Both targets may be the same. As Cankerous Thirst resolves, you decide whether to apply either effect.

Cankerous Thirst : règles, fonctionnement et interactions (MTG)

Cankerous Thirst is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

If was spent to cast this spell, you may have target creature get -3/-3 until end of turn. If was spent to cast this spell, you may have target creature get +3/+3 until end of turn. (Do both if was spent.)

How it works : Cankerous Thirst

Original English text — Wizards of the Coast / Scryfall

#1August 1, 2008· Wizards of the Coast
The spell cares about what mana was spent to pay its total cost, not just what mana was spent to pay the hybrid part of its cost.
No other card is named in this ruling.
#2August 1, 2008· Wizards of the Coast
The spell checks on resolution to see if any mana of the stated colors was spent to pay its cost. If so, it doesn't matter how much mana of that color was spent.
No other card is named in this ruling.
#3August 1, 2008· Wizards of the Coast
If the spell is copied, the copy will never have had mana of the stated color paid for it, no matter what colors were spent on the original spell.
No other card is named in this ruling.
#4August 1, 2008· Wizards of the Coast
The spell cares about what mana was spent to pay its total cost, not just what mana was spent to pay the hybrid part of its cost.
No other card is named in this ruling.
#5August 1, 2008· Wizards of the Coast
When you cast the spell, you choose its targets before you pay for it.
No other card is named in this ruling.
#6August 1, 2008· Wizards of the Coast
The spell checks on resolution to see if any mana of the stated colors was spent to pay its cost. If so, it doesn't matter how much mana of that color was spent.
No other card is named in this ruling.
#7August 1, 2008· Wizards of the Coast
If the spell is copied, the copy will never have had mana of the stated color paid for it, no matter what colors were spent on the original spell.
No other card is named in this ruling.
#8August 1, 2008· Wizards of the Coast
As you cast Cankerous Thirst, you must target a creature for the first effect and you must target a creature for the second effect. Both targets may be the same. As Cankerous Thirst resolves, you decide whether to apply either effect.
No other card is named in this ruling.