Siren Reaver
Creature — Siren Pirate
Raid — This spell costs 
less to cast if you attacked this turn.
Flying
"Prepare to be boarded."
Tomasz Jedruszek
Rivals of Ixalan (RIX)
• #54Rulings
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.
(wotc • 2024-11-08)
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.
(wotc • 2024-11-08)
Rulings
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.
(wotc • 2024-11-08)
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.
(wotc • 2024-11-08)