You choose whether each token is attacking the player or a planeswalker they control as the token is created. If it's attacking a planeswalker, you choose which one. You can't have any of the tokens attack a battle.
Scurry of Squirrels
The term "defending player" in the myriad rules (or any other ability of an attacking creature) refers to the player the creature with myriad was attacking, the controller of the planeswalker it was attacking, or the protector of the battle it was attacking at the time the ability resolves. If that creature is no longer attacking, it refers to the appropriate player based on who or what the creature was last attacking.
If an instance of myriad creates more than one token for any given player (due to an effect such as the one Doubling Season creates), you may choose separately for each token whether it's attacking the player or a planeswalker they control.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Izzy
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
