Raid — When this creature enters, if you attacked this turn, add .
Raid abilities care only that you attacked with a creature. It doesn't matter how many creatures you attacked with or which player, planeswalker, or battle those creatures attacked.
Raid abilities evaluate the entire turn to see if you attacked with a creature. That creature doesn't have to still be on the battlefield. Similarly, the player, planeswalker, or battle it attacked doesn't have to still be in the game or on the battlefield.
Mardu Warshrieker's raid ability isn't a mana ability even though it adds mana. It uses the stack and can be responded to.
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