Yusri, Fortune's Flame — ruling 1

When you cast a spell without paying its mana cost, you may still pay additional costs. If any additional costs are required, you must pay them.

Yusri, Fortune's Flame — ruling 2

If an effect allows you to cast a spell with {X} in its cost without paying its mana cost, you must choose 0 for the value of X.

Yusri, Fortune's Flame : règles, fonctionnement et interactions (MTG)

Yusri, Fortune's Flame 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

Flying Whenever Yusri attacks, choose a number between 1 and 5. Flip that many coins. For each flip you win, draw a card. For each flip you lose, Yusri deals 2 damage to you. If you won five flips this way, you may cast spells from your hand this turn without paying their mana costs.

How it works : Yusri, Fortune's Flame

Original English text — Wizards of the Coast / Scryfall

#1June 18, 2021· Wizards of the Coast
When you cast a spell without paying its mana cost, you may still pay additional costs. If any additional costs are required, you must pay them.
No other card is named in this ruling.
#2June 18, 2021· Wizards of the Coast
If an effect allows you to cast a spell with in its cost without paying its mana cost, you must choose 0 for the value of X.
No other card is named in this ruling.