Vexing Puzzlebox
Artifact
Whenever you roll one or more dice, put a number of charge counters on this artifact equal to the result.
: Add one mana of any color. Roll a d20.
, Remove 100 charge counters from this artifact: Search your library for an artifact card, put that card onto the battlefield, then shuffle.
Illustrated by
Commander Legends: Battle for Baldur's Gate#343MythicEnglishLegality
Rulings
If an effect instructs you to roll one or more dice and add some number to that roll, the result is the total after adding that number.
If an effect instructs you to roll more than one die and ignore one or more of them, the result is only what wasn't ignored.
In a game of Planechase, the result of rolling the planar die is not a number and does not cause Vexing Puzzlebox's first ability to put charge counters on it.
Even though it includes rolling a die, Vexing Puzzlebox's second ability is a mana ability. It does not use the stack and cannot be responded to.