Gravity Sphere, and Stormtide Leviathan

Prerequisites

• Gravity Sphere on the battlefield
• Stormtide Leviathan on the battlefield

Steps

1. Gravity Sphere causes all creatures to lose flying
2. Stormtide Leviathan prevents creatures from attacking unless they have flying and/or islandwalk
3. Since no creatures will have flying, only creatures with islandwalk can attack

Results

• Creatures without islandwalk cannot attack