Death's Shadow

• WWizards of the Coast2020-08-07
  Official Ruling
  If your life total is negative, X is considered to be 0.
• WWizards of the Coast2020-08-07
  Official Ruling
  Death's Shadow's ability applies only while Death's Shadow is on the battlefield. In all other zones, its power and toughness are 13.
• WWizards of the Coast2020-08-07
  Official Ruling
  In a Two-Headed Giant game, your life total is your team's life total.
• WWizards of the Coast2020-08-07
  Official Ruling
  The value of X changes as you gain and lose life. It's not locked in as Death's Shadow enters the battlefield.

Rulings via Scryfall