Ritual of Soot — ruling 1

Tokens that aren't a copy of something else don't have a mana cost. Anything without a mana cost normally has a mana value of 0.

Ritual of Soot — ruling 2

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

Ritual of Soot : règles, fonctionnement et interactions (MTG)

Ritual of Soot 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

Destroy all creatures with mana value 3 or less.

How it works : Ritual of Soot

Original English text — Wizards of the Coast / Scryfall

#1October 5, 2018· Wizards of the Coast
Tokens that aren't a copy of something else don't have a mana cost. Anything without a mana cost normally has a mana value of 0.
No other card is named in this ruling.
#2October 5, 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.