Cheapest priced copy (Duskmourn: House of Horror Commander): $6.49 at Card Kingdom, near mint, their price list as of .
Sphere of Safety 
Enchantment · Uncommon · Return to Ravnica · #24
Creatures can't attack you or planeswalkers you control unless their controller pays {X} for each of those creatures, where X is the number of enchantments you control.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
8 printings · $6.49 to $32.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Commander 2016 | 77 | Uncommon | $7.49 | — |
| Duskmourn: House of Horror Commander | 104 | Uncommon | $6.49 | — |
| Return to Ravnica | 24 | Uncommon | $7.49 | $9.99 |
| Ravnica Remastered | 447 | Uncommon | $6.49 | $9.99 |
| Secret Lair Drop | 280 | Rare | $17.99 | $14.99 |
| Secret Lair Drop | 588 | Rare | — | $9.49 |
| Secret Lair Drop | 2316 | Rare | $13.99 | $20.99 |
| Secret Lair Drop | 2331 | Rare | — | $32.99Out of stock |
One ruling from Wizards of the Coast
- 1 October 2012If you control Sphere of Safety, your opponents can choose not to attack with a creature with an ability that says it attacks if able.