Tattered Mummy

• WWizards of the Coast2018-07-13
  Official Ruling
  In a Two-Headed Giant game, the triggered ability of Tattered Mummy causes the opposing team to lose 4 life.
• WWizards of the Coast2018-07-13
  Official Ruling
  If your life total is brought to 0 or less at the same time that Tattered Mummy is dealt lethal damage, you lose the game before its triggered ability goes on the stack.

Rulings via Scryfall