Pernicious Deed — ruling 1

If a permanent has {X} in its mana cost, X is considered to be 0.

Pernicious Deed — ruling 2

A token has a mana value of 0 unless it is copying something else.

Pernicious Deed : règles, fonctionnement et interactions (MTG)

Pernicious Deed is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

, Sacrifice this enchantment: Destroy each artifact, creature, and enchantment with mana value X or less.

How it works : Pernicious Deed

Original English text — Wizards of the Coast / Scryfall

#1March 16, 2018· Wizards of the Coast
If a permanent has in its mana cost, X is considered to be 0.
No other card is named in this ruling.
#2March 16, 2018· Wizards of the Coast
A token has a mana value of 0 unless it is copying something else.
No other card is named in this ruling.