Historical Rules · 5 February 2021
Rule 901.8
Official source text from the 5 February 2021 Rules release
Planechase games have an inherent triggered ability known as the “planeswalking ability.” The full text of this ability is “Whenever you roll {PW}, planeswalk.” (See rule 701.24, “Planeswalk.”) This ability has no source and is controlled by the player whose planar die roll caused it to trigger. This is an exception to rule 113.8.