Sphere of Safety
Enchantment
Creatures can't attack you or planeswalkers you control unless their controller pays 
for each of those creatures, where X is the number of enchantments you control.
The Rakdos believe that all are eager to join their revels, even when told otherwise.
Illustrated by
Ravnica Remastered#447UncommonEnglishLegality
Rulings
Oct 1, 2012
If you control Sphere of Safety, your opponents can choose not to attack with a creature with an ability that says it attacks if able.