Mindblade Render

• WWizards of the Coast2018-06-08
  Official Ruling
  Mindblade Render's ability triggers if a Warrior an opponent controls deals combat damage to another player who's also your opponent. You can't choose not to draw a card or lose 1 life if this happens.
• WWizards of the Coast2018-06-08
  Official Ruling
  Mindblade Render's ability triggers only once, regardless of how many opponents were dealt damage, how much damage they were dealt, or how many Warriors dealt damage.

Rulings via Scryfall