Irresistible Prey

• WWizards of the Coast2010-06-15
  Official Ruling
  If the targeted creature is an illegal target by the time Irresistible Prey resolves, the spell doesn’t resolve. You won’t draw a card.
• WWizards of the Coast2010-06-15
  Official Ruling
  If the affected creature attacks, the defending player must assign at least one blocker to it during the declare blockers step, unless that player controls no creatures that could block it.
• WWizards of the Coast2010-06-15
  Official Ruling
  You can target a creature you don’t control or that otherwise couldn’t attack that turn.
• WWizards of the Coast2010-06-15
  Official Ruling
  The creature affected by Irresistible Prey doesn’t have to attack that turn.

Rulings via Scryfall