As Persistent Marshstalker returns to the battlefield because of its triggered ability, you choose which player, planeswalker, or battle it's attacking. It doesn't have to attack the same player, planeswalker, or battle as your other Rats.
2024-07-26
Although Persistent Marshstalker's last ability causes it to enter attacking, it was never declared as an attacking creature. Abilities that trigger whenever a creature attacks won't trigger when it enters attacking.
This creature gets +1/+0 for each other Rat you control.
Threshold — Whenever you attack with one or more Rats, if there are seven or more cards in your graveyard, you may pay . If you do, return this card from your graveyard to the battlefield tapped and attacking.
. If you do, return this card from your graveyard to the battlefield tapped and attacking.