Stalking Wolf

Q: I attack a battlefield with only a (Poro) unit. In the showdown, my enemy plays a spell that will kill my (Poro) unit. I react by playing <<Stalking Wolf>> with Ambush and choose to kill my (Poro) as its cost. Is this a legal play?

Rules for Context - Reminder text, 822.3.

A: It is NOT a legal play to the battlefield you are attacking.

However, it is a legal play as long as Stalking Wolf is played to a different battlefield than the one where the Poro is located.

(Stalking Wolf is being looked at to receive updated wording in the future.)