901.9 Any time the active player has priority and the stack is empty, but only during a main phase of their turn, that player may roll the planar die. Taking this action costs a player an amount of mana equal to the number of times they have previously taken this action on that turn. This is a special action and doesn’t use the stack. Note that this number won’t be equal to the number of times the player has rolled the planar die that turn if an effect has caused the player to roll the planar die that turn. (See rule 116.2i.)
901.9a
If the die roll is a blank face, nothing happens. The active player gets priority.
901.9b
If the die roll is the chaos symbol, chaos ensues (see rule 311.7). The active player gets priority.
(refs: 311.7)
901.9c
If the die roll is the Planeswalker symbol, the “planeswalking ability” triggers and is put on the stack. The active player gets priority. (See rule 901.8.)
(refs: 901.8)
901.9d
Rolling the planar die will cause any ability that triggers whenever a player rolls one or more dice to trigger. However, any effect that refers to a numerical result of a die roll, including ones that compare the results of that roll to other rolls or to a given number, ignores the rolling of the planar die. See 706, “Rolling a Die.”