Spread the Sickness
Mirrodin Besieged — common
Sorcery
Spread the Sickness rulings:
2013-07-01: If the creature regenerates or has indestructible when Spread the Sickness resolves, you’ll still proliferate.
2011-06-01: If the creature is an illegal target when Spread the Sickness tries to resolve, the spell doesn’t resolve. You won’t proliferate.