Mystic Decree, and Stormtide Leviathan

Prerequisites

• Mystic Decree on the battlefield
• Stormtide Leviathan on the battlefield

Steps

1. Mystic Decree causes all creatures to lose flying and islandwalk
2. Because Stormtide Leviathan prohibits creatures without flying or islandwalk from attacking, no creatures can attack

Results

• Creatures cannot attack