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• WOTC Official Reminder Textofficial rules
  Convoke — Your creatures can help cast this spell. Each creature you tap while casting this spell pays for or one mana of that creature's color.

• WWizards of the Coast2024-01-12
  Official Ruling
  You can tap any untapped creature you control to convoke a spell, even one you haven't controlled continuously since the beginning of your most recent turn.
• WWizards of the Coast2024-01-12
  Official Ruling
  When using convoke to cast a spell with in its mana cost, first choose the value for X. That choice, plus any cost increases or decreases, will determine the spell's total cost. Then you can tap creatures you control to help pay that cost. For example, if you cast Chord of Calling (a spell with convoke and mana cost ) and choose X to be 3, the total cost is . If you tap two green creatures and two red creatures, you'll have to pay .
• WWizards of the Coast2024-01-12
  Official Ruling
  Because convoke isn't an alternative cost, it can be used in conjunction with alternative costs.
• WWizards of the Coast2024-01-12
  Official Ruling
  Tapping an untapped creature that's attacking or blocking to convoke a spell won't cause that creature to stop attacking or blocking.
• WWizards of the Coast2024-01-12
  Official Ruling
  If a creature you control has a mana ability with in the cost, activating that ability while casting a spell with convoke will result in the creature being tapped before you pay the spell's costs. You won't be able to tap it again for convoke. Similarly, if you sacrifice a creature to activate a mana ability while casting a spell with convoke, that creature won't be on the battlefield when you pay the spell's costs, so you won't be able to tap it for convoke.
• WWizards of the Coast2024-01-12
  Official Ruling
  When calculating a spell's total cost, include any alternative costs, additional costs, or anything else that increases or reduces the cost to cast the spell. Convoke applies after the total cost is calculated. Convoke doesn't change a spell's mana cost or mana value.
• WWizards of the Coast2024-01-12
  Official Ruling
  Tapping a multicolored creature using convoke will pay for or one mana of your choice of any of that creature's colors.

Rulings via Scryfall